BLAHODATNE, Ukraine (AP) — Three days before Ukraine holds a key presidential vote, pro-Russia insurgents attacked a military checkpoint Thursday in eastern Ukraine, killing 13 troops in the deadliest raid yet in weeks of fighting, Ukraine's leader said
A rebel group who claimed responsibility for the attack said one of its own was also killed.
The rebels attacked the checkpoint near the town of Volnovakha, firing automatic weapons and rocket-propelled grenades, acting President Oleksandr Turchynov said
AP journalists saw 11 dead Ukrainian soldiers scattered in a field near the village of Blahodatne, outside Volnovakha, 30 kilometers (20 miles) south of the major city of Donetsk.
Witnesses including a medical worker said over 30 other Ukrainian troops were wounded in the attack and some of them were in grave condition. All the wounded were being treated at nearby medical facilities.
The Ukrainian Defense Ministry said the attackers hit an ammunition section in one of the vehicles, which exploded in a fireball.
Three charred Ukrainian armored infantry vehicles, their turrets blown away, and several burned trucks stood at the road site in Blahodatne. Scorched bodies, apparently burned by the explosion and fire, were scattered near the vehicles.
Acting Prime Minister Arseniy Yatsenyuk blamed Russia for backing the rebels in the Donetsk and Luhansk regions, which have declared independence from the government in Kiev. He issued a call for an urgent session of the U.N. Security Council.
Thursday's carnage cast a shadow over Ukraine's upcoming presidential vote on Sunday, which separatists in the east have pledged to derail. Authorities in Kiev see the vote as a chance to defuse tensions and stabilize the country. Even so, they have admitted it will be impossible to stage the vote in some eastern areas where election officials and voters have faced intimidation and sometimes death threats from the rebels.
Residents said attackers used an armored bank truck, which the unsuspecting Ukrainian soldiers waved through, and then mowed them down at point-blank range. Their account couldn't be independently confirmed.
In the town of Horlivka, a masked rebel commander claimed responsibility for the raid and showed an array of seized Ukrainian weapons. There was no way to independently confirm his claim.
"We destroyed a checkpoint of the fascist Ukrainian army deployed on the land the Donetsk Republic," said the commander, who wore a balaclava and identified himself by his nom de guerre, "Bes," Russian for "demon." He said one of his men also was killed.
"The weapons you see here have been taken from the dead, they are trophies," the rebel commander said, showing automatic and sniper rifles, rocket grenade launchers and bulletproof vests in the courtyard of the occupied Horlivka police headquarters.
"People living in western Ukraine: Think about where you are sending your brothers, fathers and sons, and why you need any of this," he added.
Many in the east resent the government in Kiev, which came to power after a pro-Russian president fled in February following months of protests, seeing it as nationalists bent on repressing Russian-speakers. But many locals also have grown increasingly exasperated with the rebels, whom they blame for putting civilians in the crossfire.
In the village of Semenovka on the outskirts of Slovyansk, artillery shelling badly damaged several houses Thursday.
Zinaida Patskan, 80, had her roof torn away by an explosion that also shattered a wall. She said she was hiding under a kitchen table with her cat, Timofey, when the shelling came.
"Why they are hitting us?" she said, bursting into tears. "We are peaceful people!"
About 100 Semenovka residents later vented their anger against the central government, demanding that Ukrainian forces cease their offensive against the separatists and withdraw from the region. Speakers at the rally also urged residents to boycott the presidential vote.
While fighting raged in Ukraine, Russia's Defense Ministry said Thursday its forces were leaving the regions near Ukraine as part of a massive military pullout ordered by President Vladimir Putin. It said four trainloads of weapons and 15 Il-76 heavy-lift transport planes had already left the Belgorod, Bryansk and Rostov regions.
NATO had estimated Russia has 40,000 troops along the border with Ukraine.
Gen. Philip Breedlove, NATO's supreme commander in Europe, told reporters in Brussels that some Russian military movements had been detected but it was too early to assess their size or importance. He said a very large and capable Russian force still remained close to Ukraine.
In Kiev, Yatsenyuk described Russia's announcement of troops pull-out as "bluffing."
"Even if the troops are withdrawing, Russian authorities are still assisting the armed terrorists who were trained in Russia," he said.
Russian Foreign Ministry spokesman Alexander Lukashevich on Thursday rejected Yatsenyuk's claims of Russian interference in the east as unfounded and denounced his call for a U.N. Security Council meeting as a "propaganda."
Putin's pullout order and his remarks welcoming Ukraine's presidential election Sunday reflected an attempt to ease tensions with the West over Ukraine and avoid a new round of Western sanctions. He has ignored the plea of some of the rebels in eastern Ukraine to join Russia.
The United States and the European Union imposed travel bans and asset freezes on members of Putin's entourage after Russia annexed Crimea in March. The U.S. and EU have warned that more crippling sanctions against entire sectors of the Russian economy could follow if Russia tries to grab more land from Ukraine or attempts to derail Ukraine's election.
Russia has pushed for guarantees that Ukraine will not join NATO and has advocated constitutional reforms that would give broader powers to Ukraine's regions, which would maintain Moscow's clout in the Russian-speaking eastern regions that form the nation's industrial heartland.
The Kremlin, meanwhile, angrily protested the detention of journalists working for Russian media outlets in Ukraine. Graham Phillips, a Briton working for state-controlled English language television station RT, was detained earlier this week by Ukrainian forces, but was released Wednesday.
Two correspondents with the Moscow-based Life News television, who were also detained, have remained in Ukrainian custody and face accusations of aiding armed insurgents — a claim Putin has dismissed as "rubbish and nonsense."
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Leonard reported from Horlivka, Ukraine. Dmitry Kozlov in Blahodatne, Ukraine, Nataliya Vasilyeva in Kiev, Vladimir Isachenkov in Moscow, Predrag Milic in Podgorica, Montenegro, and John-Thor Dahlburg in Brussels contributed to this report.