Abuja (AFP) - Nigeria's President Goodluck Jonathan on Tuesday said the military was gaining the upper hand against Boko Haram, despite two bombings in the country's north that killed at least 27.

"The President assures all Nigerians, and the people of the northeastern states in particular, that the days of mourning victims of incessant terrorist attacks in the country will soon be over as the tide has now definitely turned against Boko Haram," his office said in an emailed statement.

Jonathan's statement came after two separate bombings at bus stations in the north's biggest city, Kano, and the commercial capital of Yobe state, Potiskum.

The head of state, who has been criticised for his inability to end the six-year insurgency, described the attacks as the "callous bombing of soft targets".

Nigeria's military on Saturday claimed it had retaken the fishing town of Baga, scene of what is thought to have been Boko Haram's worst massacre in which hundreds, if not more, were killed.

Last week, soldiers retook the garrison town of Monguno, also in Borno state, while Chadian troops, deployed as part of a wider, regional fight against the militants, have bombed militant positions.

The offensive against the Islamists also involves troops from Cameroon and Niger in a reflection of fears about the threat from the group to regional security.

But despite the apparent successes, violence has continued both within Nigeria and also spread to Niger and Chad.

Nigeria had been due to go to the polls on February 14 but the vote was delayed by six weeks to give the military more time to secure and stabilise the northeast, which has seen the worst violence.

The decision by the country's electoral commission was seen by some as a way for Jonathan, who is seeking a second, four-year term, to revive his campaign.

He had been seen as neck-and-neck with the main opposition candidate, with the chance that his ruling party would be beaten for the first time since Nigeria returned to civilian rule in 1999.

Some have seen the six-week deadline as unrealistic but Jonathan said the military, "supported with new platforms, equipment and logistics", would be successful "in the shortest possible time".

A Houthi militia truck is seen at the yard of the Republican Palace in Sanaa February 25, 2015. Armed men from Yemen's newly dominant Houthi group took over a special forces army base in the capital Sanaa early on Wednesday, soldiers there said. REUTERS/Khaled Abdullah

By Mohammed Ghobari

SANAA (Reuters) - Armed men from Yemen's newly dominant Houthi group took over a special forces army base in the capital Sanaa early on Wednesday, soldiers there said.

The clashes, which lasted around six hours, started late on Tuesday when Houthis shelled the camp with heavy weapons, soldiers from the camp said. At least 10 people were killed.

The troops had been trained and equipped by the United States as an elite counterterrorism unit during the rule of ex-president Ali Abullah Saleh, who was ousted by Arab Spring protests in 2011, military sources told Reuters.

Houthi militiamen seized Sanaa in September, eventually leading President Abd-Rabbu Mansour Hadi to flee to Aden this week where he seeks to set up a rival center of power.

For more than a decade the United States has watched with alarm as Al Qaeda in the Arabian Peninsula - the most powerful arm of the global militant group - has grown in Yemen as the political chaos has mounted.

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A Houthi militiaman looks on as he stands at the yard of the Republican Palace in Sanaa February 25, …

The U.S. military trained and kitted out Yemeni soldiers under Saleh, and under Hadi the CIA has stepped up drone strikes aimed at killing suspected militants.

U.S. officials have expressed concern that the rule of the resolutely anti-American Shi'ite Muslim Houthis will harm their counterterrorism efforts in a country that shares a long border with Saudi Arabia, the world's oil exporter.

Yemen's Sunni Gulf neighbors have decried the Houthi takeover as a coup, and the head of the Gulf Cooperation Council Abdullatif al-Zayyani arrived in Aden to meet Hadi on Wednesday, political sources there said.

The power struggle between the Houthis in Sanaa and Hadi in Aden casts more doubt on U.N.-sponsored talks to resolve Yemen's crisis peacefully, and exacerbates sectarian and regional splits which may plunge the country into civil war.

The Houthis said on Tuesday that Hadi had lost his legitimacy as head of state and was being sought as a fugitive from justice.

(Additional reporting By Mohammed Mukhashaf and Noah Browning; Writing by Maha El Dahan; Editing by Alison Williams)

Kiev (AFP) - A UN-backed ceasefire showed signs of taking hold in Ukraine on Wednesday, but tensions remained high after the US accused Russia of "lies" and Britain ordered a small troop deployment to train Kiev's forces.

Russia in turn has warned it could within days cut off gas supplies to Ukraine -- and, by extension, to parts of the European Union.

For the first time since the European-brokered truce came into force February 15, no deaths were reported in Ukraine's war zone by either side for the past 24 hours.

"Over the past day, one soldier was wounded but there were no dead," Ukrainian military spokesman Andriy Lysenko told journalists in Kiev.

There was still no confirmation, though, from the Organization for Security and Cooperation in Europe (OSCE) of a pull-back of heavy weapons from the frontline -- the other key plank of the truce.

Rebels insisted they were withdrawing artillery, rocket launchers and tanks from some areas, and journalists saw a column of howitzer guns being driven along a road near the separatist stronghold of Donetsk.

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The key industrial hub of Mariupol has become the latest hotspot in the conflict in east Ukraine, st …

"We are following orders to pull back heavy weapons, but the Ukrainians aren't," a rebel commander going by the nickname "Khoroshii" told AFP.

But the OSCE mission in Ukraine said in a statement the warring sides had not provided the information needed to determine what, if any, arms withdrawals have occurred.

- Exasperation with Russia -

Kiev says it will not carry out an arms pull-back until a full and "comprehensive" ceasefire is observed and has accused Russia of continuing to send military hardware in to bolster the rebels.

The West has thrown its hopes of finding a negotiated solution to Ukraine's 10-month conflict fully behind the truce, which last week won unanimous backing from the UN Security Council.

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Pro-Russian rebels move heavy-artillery from close the eastern Ukrainian town of Starobecheve, on Fe …

But continued breaches by rebel forces -- especially their assault on Debaltseve, a strategic transport hub, and a build-up and attacks on Ukrainian army positions near the port city of Mariupol -- have exasperated the EU and US.

US Secretary of State John Kerry on Tuesday launched his most scathing accusation to date over Russia's alleged involvement in the conflict.

"They have been persisting in their misrepresentations -- lies -- whatever you want to call them -- about their activities there to my face, to the face of others, on many different occasions," he told US lawmakers.

He said Russia was also engaging in "the most overt and extensive propaganda exercise that I've seen since the very height of the Cold War."

- 'Worst crisis since Cold War' -

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The United States and EU nations blame Russia for fomenting the 10-month-old insurgency in east Ukra …

British Prime Minister David Cameron separately announced his country was sending up to 75 soldiers to Ukraine on a "training mission", with some leaving for Kiev this week. He said they would not be sent to the conflict zone.

Cameron urged the EU to look at wide-ranging sanctions on Russia's economy, which is already toppling into recession because of a drop in oil prices.

Moscow's denials of backing the insurgency have been dismissed by the West.

The United States says it has evidence of Russian military deployments, and pointed to similar denials -- later dropped by Moscow -- over Russian troop involvement ahead of last year's annexation of Crimea.

Russia is flexing its muscles in readiness for any additional sanctions against it. Its state-run gas giant Gazprom has warned it could cut off supplies to Ukraine, amid a dispute over payment.

President Vladimir Putin said Wednesday that Ukraine had paid only enough "for three or four days' gas supplies. Unless there is a prepayment, Gazprom... will terminate the supply," according to the Interfax news agency.

Much of the gas that flows through Ukraine goes on to supply the EU market.

Putin, in televised comments, also claimed Ukraine had cut off gas supplies to separatist-held territories in the east in what "smacks of genocide."

The instability is torpedoing Ukraine's fragile economy. The country's central bank on Wednesday increased currency controls in a bid to stop a free-fall of the national money, the hryvnia.

A Kurdish Peshmerga fighter takes up position with weapon at the frontline against the Islamic State, on the outskirts of Mosul January 26, 2015. REUTERS/Azad Lashkari

By Tom Perry and Suleiman Al-Khalidi

BEIRUT/AMMAN (Reuters) - Kurdish militia pressed a big offensive against Islamic State in northeast Syria on Wednesday, cutting one of its supply lines from Iraq, as fears mounted for dozens of Christians abducted by the hardline group that recently beheaded 21 Egyptian Copts.

At least 90 Assyrian Christians were seized from villages in Hasaka province in a mass abduction coinciding with the offensive in the same region by Kurdish forces backed by U.S.-led air strikes, according to the Syrian Observatory for Human Rights, which tracks the conflict.

The Syriac National Council of Syria put the figure as high as 150. Hundreds more Christians have fled to the two main cities in Hasaka province, according to the Syriac council and the Syrian Observatory for Human Rights, which is tracking the conflict.

Islamic State has killed members of religious minorities and Sunni Muslims who do not swear allegiance to its self-declared "caliphate". The group last week released a video showing its members beheading 21 Egyptian Coptic Christians in Libya.

The abductions in Syria follow advances by Kurdish forces against Islamic State in areas of the northeast near the Iraqi border - an area of vital importance to the group as one of the bridges between land it controls in Iraq and Syria.

"They want to show themselves strong, playing on the religion string, at a time when they are being hit hard," said Rami Abdulrahman, who runs the British-based Observatory, speaking by telephone.

The Syrian Kurdish YPG militia, backed by U.S.-led air strikes, last month drove Islamic State from the Syrian town of Kobani, since when further signs of strain have been seen in the group's ranks.

KURDS INFLICT NEW LOSSES ON ISLAMIC STATE

The Assyrian Christians were taken from villages near the town of Tel Tamr, some 20 km (12 miles) to the northwest of the city of Hasaka. There has been no word on their fate. There have been conflicting reports on where the Christians had been taken.

"These were peaceful villages that had nothing to do with the battles," said Nasir Haj Mahmoud, a Kurdish official in the YPG militia in northeastern Syria, speaking by telephone from the city of Qamishli.

Some Christians are fighting under the umbrella of the YPG in Hasaka province, but not in that area, he added.

The new Kurdish offensive launched at the weekend was focused on dislodging Islamic State from areas some 100 km (60 miles) further to the east, including Tel Hamis, a town that is one of its strongholds.

The Observatory said at least 132 Islamic State fighters had been killed in the fighting since Feb. 21. Mahmoud, the Kurdish official, said seven members of the Kurdish YPG militia had been killed, including one foreigner.

He said he did not know where the foreigner was from, but British and U.S. citizens have gone to fight with the YPG against Islamic State. A second Kurdish official confirmed a foreigner was "martyred" but declined to give further details.

In a telephone interview from the city of Qamishli, he said the YPG had cut a main road linking Tel Hamis with al-Houl, a town just a few kilometers from the Iraqi border.

"This is the main artery for Daesh," he said, using an acronym for Islamic State. The Kurdish YPG militia had seized more than 100 villages from Islamic State in the area, he added.

"We believe we will finish the battle of Tel Hamis in this campaign," he added.

Videos posted online by the YPG showed Kurdish fighters firing at Islamic State positions in Hasaka.

OFFENSIVE WELL-ORGANIZED

The offensive underlines the emergence of the well-organized Syrian Kurdish militia as the main partner for the U.S.-led alliance against Islamic State in Syria.

Mainstream rebels fighting President Bashar al-Assad have mostly been eclipsed by jihadists, complicating a U.S. plan to train and equip Syrian opposition forces to fight Islamic State.

Washington has shunned the idea of partnering with the Damascus government, seeing Assad as part of the problem. Syrian government forces, waging a separate campaign against Islamic State, have made advances against the group in Hasaka in recent weeks.

The latest fighting in Hasaka is one piece of the Syrian war that is about to enter its fifth year and is being fought by an array of forces on multiple frontlines.

Government forces and allied militia are waging their own campaign against Islamic State, while also battling other insurgents including mainstream rebels and the al Qaeda-linked Nusra Front in western areas that are mostly under state control.

A large offensive by government forces backed by the Lebanese group Hezbollah earlier this month made swift progress in the south before slowing, while an attempt to encircle rebel-held areas of the northern city of Aleppo last week was repulsed, according to the Observatory.

The U.S.-based Human Rights Watch accused the Syrian government on Tuesday of carrying out hundreds of indiscriminate aerial attacks in the past year, most with barrel bombs, in defiance of a United Nations Security Council demand to stop.

(Additional reporting by Nadine Malla and Mariam Karouny; Writing by Tom Perry; Editing by Nick Macfie and Peter Millership)