BYLBASIVKA, Ukraine -- Within hours of an Easter morning shootout at a checkpoint manned by pro-Russia insurgents in eastern Ukraine, Russia's Foreign Ministry issued a statement blaming militant Ukrainian nationalists and Russian state television stations aired pictures of supposed proof of their involvement in the attack that left at least three people dead.
The Ukrainian Security Service, however, said the attack was staged by provocateurs from outside the country. And the presented evidence -- particularly a pristine business card said to have been left behind by the attackers -- was met with widespread ridicule in Ukraine, where it soon had its own Twitter hashtag.
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The armed clash early Sunday near the city of Slovyansk appeared to be the first since an international agreement was reached last week in Geneva to ease tensions in eastern Ukraine, where armed pro-Russia activists have seized government buildings in at least 10 cities.
Ukraine's new leaders and many in the West fear that such clashes could provide a pretext for Russia to seize more Ukrainian territory.
Russia, which annexed the Crimean Peninsula last month, has tens of thousands of troops along its border with Ukraine. Russian officials, including President Vladimir Putin, originally said the troops were there for military exercises, but Putin's spokesman on Saturday acknowledged that some were there because of instability in eastern Ukraine.
The self-proclaimed mayor of Slovyansk appealed to Putin on Sunday to send in peacekeeping troops to protect Russian speakers from Ukrainian nationalists.
"They want to make us slaves. They don't talk to us, but simply kill us," Vyacheslav Ponomaryov said during a news conference in Slovyansk shown on Rossiya state television.
Yuri Zhadobin, who coordinates the pro-Russia unit manning the checkpoint in the village of Bylbasivka, told The Associated Press he was with about 20 men celebrating Easter when unknown men drove up in four vehicles and opened fire about 3 a.m.
"We began to shoot back from behind the barricades and we threw Molotov cocktails at them," Zhadobin said. Two of the vehicles caught fire and the attackers fled in the other two, he said.
The Ukrainian Interior Ministry's office in the eastern Donetsk region said three people died in the attack and three others were wounded. The statement said some of the attackers were also killed or wounded, but the number wasn't known. Russian state television reported that two of the attackers were killed.
In Moscow, the Russian Foreign Ministry quickly blamed the clash on the Right Sector, a nationalist Ukrainian group that has supported the pro-Western interim government in Kiev, the capital.
But a spokesman for Right Sector, Artyom Skoropatskiy, denied any involvement in Sunday's shootout, which he called a provocation staged by Russian special services.
Ukraine's Security Service also called the attack a "cynical provocation" staged from "the outside."
Russian state and other Kremlin-friendly television channels showed pictures of items said to have been seized from the attackers and the two captured vehicles, which were pockmarked by bullets and gutted by fire. The items included weapons, ammunition, maps and the business card of Right Sector leader Dmytro Yarosh.
This gave rise to a flood of humorous posts on Ukrainian Twitter with the hashtag "VizitkaYarosha," or Yarosh's business card.
A man said to be a member of Right Sector and one of the attackers was later paraded before the television cameras in the custody of an insurgent wearing camouflage fatigues and a black balaclava. The man said he would advise other Right Sector activists against coming to eastern Ukraine.
"There is a war here," he said in footage broadcast by Russia's Channel One. "People here are defending their land, defending their home and their rights."
Putin has rejected claims that Russian special forces are directing or encouraging the insurgents. Putin also has said he hopes not to send troops into eastern Ukraine, but he retains the right to intervene if necessary to protect ethnic Russians living here.
Russian state media have been feeding fears among the Russian-speaking population in eastern Ukraine that their lives are in danger because of the Right Sector.
"See what is happening?" asked Andrei Zarubin, 30, who came to the Bylbasivka checkpoint Sunday afternoon to replace those who had come under attack. "We hope that Russia will help, that Russia will protect us. Who else can we turn to for help?"
The Russian Foreign Ministry statement said the attack "proves the unwillingness of the Ukrainian authorities to restrain and disarm the nationalists and extremists."
After last week's talks in Geneva, top diplomats from Ukraine, Russia, the United States and the European Union called for an array of actions, including the disarming of militant groups and the freeing of public buildings taken over by insurgents.
Those terms quickly became a heated issue as pro-Russian armed groups that have seized police stations and other government buildings in eastern Ukraine said they would not vacate them unless the country's acting government resigned.
The insurgents say the Kiev authorities, who took power after pro-Russia Ukrainian President Viktor Yanukovych was ousted in February following months of protests, aim to suppress the country's Russian-speakers. Eastern Ukraine, which was Yanukovych's support base, has a substantial Russian-speaking population.
Russia also insists that the Kiev government should disarm members of the Right Sector, whose activists are occupying several buildings in the center of the capital, having turned them into makeshift offices.