A destroyed building with a wall painted with the black flag commonly used by Islamic State militants, is seen in the town of al-Alam March 10, 2015. REUTERS/Thaier Al-Sudani

ERBIL, Iraq (Reuters) - Islamic State has published a video purporting to show the beheading of three Kurdish peshmerga fighters in northern Iraq by militants who threatened to kill "dozens" more of those being held captive.

The six-minute clip, which appeared timed to coincide with celebrations for the Kurdish New Year, showed the peshmerga wearing orange jumpsuits being decapitated by three black-clad militants, all of whom spoke Kurdish.

The footage could not be independently verified.

The peshmerga have emerged as a key partner for the U.S.-led coalition in its campaign to "degrade and destroy" the extremist group, which they have driven back in northern Iraq with the help of airstrikes.

"To the Muslim Kurdish people: know that our war is not with you, rather it is with those who ventured into an alliance with the Safavids and crusaders to wage war on the Muslims," said one of the militants, using derogatory terms to refer to Iran and the coalition respectively. Tehran has also provided assistance to the peshmerga.

Another of the militants then directly addressed Kurdish leader Masoud Barzani: "We warned you before that for every rocket you fire on those under the care of the Islamic State, you will kill one of your prisoners with your own hands."

Kurdish forces shelled inside Mosul several days ago in what the peshmerga ministry said was retaliation for an Islamic State missile that landed in a vegetable market outside the regional capital of Erbil on Monday.

Earlier this year, a peshmerga was beheaded by a Kurdish militant in Mosul after Grad rockets were fired into the city by the Kurds.

Last month, another video was published showing captive peshmerga in cages being interviewed by a Kurdish militant.

Islamic State has previously beheaded Western aid workers and journalists as well as domestic opponents in Syria and Iraq.

More than 1,000 peshmerga have been killed in combat with Islamic State militants since they overran a third of Iraq last summer, but several hundred Kurds have joined the other side and are fighting against their ethnic kin.

Kurdish authorities last week said they had evidence the militants had used chlorine as a chemical weapon against the peshmerga on at least one occasion.

(Reporting by Omar Fahmy and Isabel Coles; Editing by Gareth Jones)

Russian President Vladimir Putin (front) addresses the audience during a festive concert marking the first anniversary of the Crimean treaty signing, with St. Basil's Cathedral seen in the background, in central Moscow, March 18, 2015. REUTERS/Mikhail Klimentyev/RIA Novosti/Kremlin View gallery Members of the Ukrainian armed forces stand guard as a convoy of the Ukrainian armed forces includin … Related Stories EU links lifting Russia sanctions to peace in Ukraine Associated Press EU leaders unlikely to tighten Russia sanctions at meeting next week: diplomatsReuters Russia accuses Kiev of tightening blockade on rebel east Reuters EU ties lifting Russia sanctions to full Ukraine peace accord Reuters EU's Russia sanctions extended to end-2015: Tusk AFP

MOSCOW (Reuters) - Russia described "sanctions rhetoric" as destructive on Friday and said it would do what is in its national interests after European Union leaders kept economic sanctions in place over the Ukraine crisis.

In comments to reporters, Kremlin spokesman Dmitry Peskov also accused Kiev of violating the terms of a peace deal for eastern Ukraine that was agreed in the Belarussian capital Minsk.

"We prefer to engage in creative matters, not destructive matters such as sanctions rhetoric. So we do not discuss sanctions and the Russian Federation will do what is in its national interests," he said.

(Reporting by Darya Korsunskaya, Writing by Timothy Heritage, Editing by Lidia kelly)

By Mohammed Ghobari and Mohammed Mukhashaf

SANAA/ADEN (Reuters) - Suicide bombers killed at least 137 worshippers and wounded hundreds more during Friday prayers at two mosques in the Yemeni capital Sanaa, in coordinated attacks claimed by Islamic State.

The attacks on mosques used by supporters of the Shi'ite Muslim Houthi fighters who control the city were the deadliest in a years-long campaign of violence in the country, where Washington has been waging a drone air war against a local branch of the Sunni Muslim militant group al Qaeda.

Sectarian unrest has increased in recent months after the Iran-backed Shi'ite fighters seized the capital last year.

Four bombers wearing explosive belts targeted worshippers in and around the crowded mosques. State news agency Saba, which is controlled by the Houthis, put the death toll at 137 and the number of wounded at 357.

Hospitals were overwhelmed, appealing for blood donors to help treat the large number of casualties.

A Reuters journalist at the Badr mosque counted at least 25 bloody bodies lying in the street and inside the building. One man carried a child in his arms.

Islamic State, the al Qaeda offshoot that controls swathes of Syria and Iraq and has been attracting followers in other countries, considers Shi'ites to be heretics.

Both groups have now rallied against the Houthis in Yemen, giving them the same enemies as the U.S.-backed government in a complex, multi-sided conflict in the Arab world's poorest country.

"Let the polytheist Houthis know that the soldiers of the Islamic State will not rest and will not stay still until they extirpate them," the group said in a statement posted by supporters on Twitter, claiming responsibility for the attacks.

"God willing, this operation is only a part of the coming flood."

Among the dead was Almortada al-Mahatwary, a leading figure in Yemen's Shi'ite Zaidi sect, the Houthi-controlled al-Masirah television channel said.

Badr mosque was hit by two bombers and two others struck a second mosque. A fifth bomber was killed when he tried to attack a mosque in Saada province, a northern Houthi stronghold, but the device went off prematurely, a security source told Reuters.

"I was going to pray at the (Badr) mosque then I heard the first explosion, and a second later I heard another one," a witness told Reuters.

Television footage showed young men in traditional Yemeni clothes carrying lifeless bodies, some dripping with blood, out of the mosque.

In Washington, the White House condemned the bombings and said it could not confirm that the attackers were affiliated with Islamic State.

HURTLING TOWARD CIVIL WAR

Yemen has been hurtling toward civil war since last year, when the Houthis seized most of the north, including Sanaa.

President Abd-Rabbu Mansour Hadi, a U.S. ally, fled the capital in February after a month imprisoned by the Houthis under house arrest and has set up a power base in the southern city of Aden.

Unidentified warplanes have attacked his Aden palace for the past two days.

Anti-aircraft guns fired on two planes that dropped bombs on an area that includes his residence on Friday. He was unharmed, sources at the presidency said.

While Yemen is one of the main bases of al Qaeda, it has not previously been known as a major base for Islamic State, the Al Qaeda offshoot also known as ISIS or ISIL.

Since last year, when Islamic State swept across northern Iraq and declared a caliphate to rule over all Muslims, militants in other countries have expressed their support for the group, although it is not clear if it actually directs them.

In Washington, White House spokesman Josh Earnest said there was no clear operational link between the people who carried out Friday's attacks in Yemen and Islamic State fighters in Iraq and Syria.

United Nations Secretary-General Ban Ki-moon condemned "the terrorist attacks" and called on all sides "to immediately cease all hostile actions and exercise maximum restraint."

Yemen has been sliding into turmoil since its long serving ruler Ali Abdullah Saleh was toppled after "Arab Spring" protests that began in 2011. Saleh is now believed to have allied himself with the Houthi fighters that he tried to crush while president.

Since fleeing the capital, Hadi has been trying to consolidate his hold over Aden to challenge the Houthis' ambitions to control the whole country.

Thirteen people were killed on Thursday when forces loyal to Hadi fought their way into Aden's international airport and wrested an adjacent military base from a renegade officer, Aden governor Abdulaziz bin Habtoor said.

(Additional reporting by Sami Aboudi in Dubai and Omar Fahmy in Cairo; Writing by Rania El Gamal; Editing by Peter Graff and John Stonestreet)

Israeli Prime Minister Benjamin Netanyahu delivers a speech to supporters at party headquarters in Tel Aviv March 18, 2015. REUTERS/Nir Elias

By Matt Spetalnick

WASHINGTON (Reuters) - U.S. President Barack Obama, who once famously said he would “always have Israel’s back,” may be rethinking that promise as aides begin weighing options in response to Prime Minister Benjamin Netanyahu’s pre-election disavowal of a two-state solution to the Middle East conflict.

Following Obama’s warning that the United States would “reassess” its relationship with Israel, the administration is not only reconsidering the diplomatic cover it has long given Israel at the United Nations but is also looking at a range of other possibilities to put pressure on its historically close ally, U.S. officials said.

Those could include becoming less active in protecting Israel in international forums and finding new ways to reinforce the message of U.S. opposition to Jewish settlement expansion.

As internal discussions proceeded on Friday, the White House appeared in no rush to lower the temperature in the worst U.S.-Israeli crisis in decades, sparked by Netanyahu’s campaign declaration that there would be no Palestinian state on his watch.

The White House made clear for a second straight day that it had little faith in Netanyahu’s effort to backtrack since winning Tuesday's election and insist he was in favor of a two-state solution, long a cornerstone of U.S. Middle East policy.

There was no sign of any imminent move to turn the administration’s heated rhetoric against Netanyahu into a tangible shift in policy.

As a result, some analysts questioned whether Washington was merely posturing to put the Israeli leader on the defensive at a time when an end-of-March deadline looms in U.S.-led nuclear diplomacy with Iran that Netanyahu vehemently opposes.

“The administration is putting everything on the table except security assistance – and this will allow Netanyahu time to walk back his comments more credibly,” said Daniel Kurtzer, former U.S. ambassador to Israel. “I would also not expect any decisions before the situation with respect to the Iran negotiations becomes clearer.”

U.S. officials privately were mindful of the risk that the diplomatic storm could drive a deeper wedge between the administration and the influential U.S. pro-Israel camp and cause problems for Obama’s fellow Democrats as the 2016 presidential campaign approaches.

One U.S. official voiced skepticism that the administration would shift its stance toward Israel in any substantive way, arguing that despite White House annoyance at Netanyahu, there would likely be too high a domestic political cost to pay for alienating pro-Israel Americans.

“I just don’t believe in the reassessment,” said this official, who spoke on condition of anonymity because of the sensitivity of U.S. relations with Israel.

But Dennis Ross, Obama’s former top Middle East adviser, said the White House pressure had other motives as well.

“There’s an effort to apply leverage to the Israelis to get the prime minister to move on some things when he has a new government formed,” Ross said, citing a U.S. wish to see Israel release frozen Palestinian tax funds and take other goodwill gestures.

RECONSIDERING U.S. SHIELD AT UN

Among the most serious risks for Israel would be a shift in Washington’s posture at the United Nations.

The United States has long stood in the way of Palestinian efforts to get a U.N. resolution recognizing its statehood, including threatening to use its veto, and has protected Israel from efforts to isolate it internationally. But European governments incensed by Netanyahu’s campaign comments against Palestinian statehood, could join in another push for such a resolution.

David Makovsky, a former member of Obama’s team in Israeli-Palestinian peace talks that collapsed last year, said the question is: “Will the U.S. consider avoiding a veto over the parameters to a final-status deal with the Palestinians?”

“There’s no doubt that this approach will lead to a firestorm between these two governments if they go forward,” said Makovsky, now at the Washington Institute for Near East Policy.

Another option under consideration cited by a U.S. official could also be controversial. A report from the administration to Congress in coming weeks about U.S. loan guarantees to Israel, including how much is used for settlements, could contain language critical of expanded construction on occupied land in the West Bank.

While the United States is not likely to reverse its opposition to the Palestinians joining the International Criminal Court next month, Washington could become less vocal in criticizing the move. Some U.S. lawmakers already have threatened to push for a cutoff of U.S. aid to the Palestinian Authority if it goes ahead with its threat to seek war crimes charges against Israel for last year’s war against Hamas in the Gaza Strip.

Other possibilities include Obama's cutting back on future one-on-one encounters with Netanyahu.

White House officials have left little doubt that Netanyahu's U.S. ambassador, Ron Dermer, has been largely frozen out by parts of the administration for his role in orchestrating Netanyahu’s speech to Congress this month against Obama’s Iran diplomacy.

(Additional reporting by Arshad Mohammed; Editing by Howard Goller)

By Emmanuel Braun

DAMASAK, Nigeria (Reuters) - Soldiers from Niger and Chad who liberated the Nigerian town of Damasak from Boko Haram militants have discovered the bodies of at least 70 people, many with their throats slit, scattered under a bridge, a Reuters witness said.

In what appeared to be an execution site for the Islamist group, the bodies were strewn beneath the concrete bridge on one of the main roads leading out of the town. At least one was decapitated.

The bodies were partially mummified by the dry desert air, while grass has began to grow around the corpses, suggesting that the killings had taken place some time ago.

Boko Haram has killed thousands of people in a six-year insurgency aimed at establishing an Islamic caliphate in northeast Nigeria. Damasak was seized by the Islamist group in November but recaptured by troops from Niger and Chad on Saturday as part of a multinational effort to wipe out the militants.

Chadian soldiers, who said the bodies were discovered on Thursday, spoke of at least 100 corpses in the area around the dry river bed. A Reuters witness was able to count at least 70.

A strong smell of decomposition in many parts of town suggested there could be more bodies concealed there, the Reuters witness said.

A trail of blackened blood was visible along the side of the bridge facing the bodies, suggesting they had been thrown off the side after being killed. Among the dead was the imam of the town.

All but around 50 of the town's residents had fled by the time Damasak was recaptured. Those who remained were mostly too old or too sick to leave.

"People were in town when they (Boko Haram) attacked, they fired at us, we ran away to the bushes but they continued to fire and chased some people to kill them," said Damasak resident Mbodou Moussa.

Chad's military spokesman Colonel Azem Bermandoa said the Chadians had asked Nigeria's military to occupy the town, which lies close to the border with Niger, and would remain there until Nigerian troops arrived.

The regional offensive was launched this year with Chad, Niger and Cameroon as Nigeria, Africa's most populous country and biggest economy, prepares for presidential elections on March 28.

At the start of this year, Boko Haram controlled around 20 local government areas, a territory the size of Belgium. With the help of its foreign allies, Nigeria's army said on Tuesday it had pushed the rebels out of all but three districts.

On Thursday, however, two security sources told Reuters that Boko Haram had killed at least 10 people in the town of Gamburu, on the border with Cameroon, demonstrating it can still attack civilians despite being forced into retreat.

President Goodluck Jonathan has been criticized for not doing enough to tackle the insurgency. His challenger Muhammadu Buhari has campaigned on a reputation for toughness gained when he was military ruler of Nigeria in the 1980s.

(Additional reporting by Abdoulaye Massalaki in Niamey; Writing by Daniel Flynn and Bate Felix; Editing by Mark Trevelyan and Grant McCool)