Just hours after Ukraine’s government declared an Easter truce, a gunfight erupted early Sunday, leaving three people dead at a checkpoint manned by a pro-Russia militia outside this restive city in eastern Ukraine.

It was the worst violence since diplomats from the United States, the European Union, Russia and Ukraine signed an agreement last week in Geneva that sought to de-escalate tension in the region.

The Russian Foreign Ministry quickly seized on the Easter Sunday clash as evidence that the new Ukrainian government could not keep order.

The new mayor of Slovyansk, meanwhile, begged Russian President Vladimir Putin to send “peacekeepers” to protect the people.

Ukraine’s leaders fear that Putin is looking for any excuse to take more direct action in the nation’s east, where many residents speak Russian and distrust the central authorities in Kiev. The Security Service of Ukraine called Sunday’s attack a “cynical provocation” staged by pro-Russia elements.

“President Putin has a dream to restore the Soviet Union, and every day he goes further and further, and God knows where is the final destination,” Ukraine’s prime minister, Arseniy Yatsen­yuk, said on NBC’s “Meet the Press.” The United States says that about 40,000 Russian troops are gathered along Russia’s border with Ukraine.

The violence came as celebrants across eastern Ukraine streamed into churches and visited historic monasteries to renew flagging spirits and to have monks bless with holy water their covered baskets containing hard-boiled eggs, sweet breads and, often, a bottle of wine.

Yet crowds were thin at the Sviatohirsk monastery on the banks of the Seversky Donets River, a 30-minute drive north of where the firefight occurred. Where usually thousands would gather to receive the Easter blessing, there were a few hundred on Sunday morning.

“People don’t know what tomorrow will be, and so we’re just happy to stay close to home,” said Sergiy, an office worker, who came to the Russian Orthodox church in downtown Donetsk rather than drive to the countryside. He declined to give his full name because of the sensitivity of the political situation.

He cited checkpoints in the area as a good reason not to venture too far.

Ukraine’s Interior Ministry said Sunday’s clash involved two groups fighting over a makeshift barricade of tires and barbed wire north of Slovyansk about 3 a.m.

Police in Slovyansk told Russia’s Interfax news agency that the three dead men belonged to the “Donetsk People’s Republic,” a political and militia group composed of separatists and others who oppose the Kiev government. The police said the men who attacked the checkpoint fled.

One of those killed was a 60-year-old bus driver, according to the Kiev Post.

It was difficult to independently establish who fought against whom. The Kiev government had declared an Easter truce, which had raised hopes that both sides would refrain from violence on the holiday.

New round of finger-pointing

The shooting stirred passions in Ukraine, where armed militias opposed to the Kiev government have taken over police stations and city halls in a cluster of eastern cities close to the Russian border.

Moscow quickly took the side of the pro-Russia activists. In a statement, the Russian Foreign Ministry said “innocent civilians” were attacked by “militants” from an ultra-nationalist, far-right organization called Right Sector, which emerged as a paramilitary group during protests in Kiev that ousted Viktor Yanukovych from the presidency in February and ushered in a pro-Western government.

“The Russian side is enraged by the militant provocation,” the Foreign Ministry declared, accusing Kiev of failing to disarm “nationalists and extremists.”

The Russians said locals had discovered weapons, aerial maps and Right Sector paraphernalia at the scene.

A spokesman for the group said it played no part in the clash and accused Russian special forces and intelligence officers of staging a provocation.

In a statement, the Security Service of Ukraine said the violence was orchestrated by pro-Russia elements trying to stir up trouble. It said evidence was planted at the scene, including new $100 bills, the business card of an ultra-nationalist leader and a World War II-era gun.

Ukrainian officials have expressed concern that Putin’s government may move military forces into eastern Ukraine, as it did in Crimea, another area with linguistic and historical ties to Russia. Moscow annexed Crimea last month.

Hours after the shooting, the mayor of Slovyansk, Vyacheslav Ponomarev, pleaded for help from Putin.

“Fascists and imperialists are trying to conquer us by killing and injuring civilians,” Ponomarev said. “They want to make slaves of us.”

Pro-Russia separatists have refused to abide by the settlement reached last week in Geneva. It offers a general amnesty to those who surrender their weapons and abandon public buildings that have been occupied in recent weeks.

It was difficult for non-Russian journalists to reach the site of the clash Sunday. One group of reporters, including a Washington Post correspondent, was turned back by an armed man. Checkpoints that were staffed last week by unarmed members of a pro-Russia militia now featured men with sidearms and rifles.

Photographs taken at the scene of the clash showed two burned vehicles pocked with bullet holes.

One of the men staffing the checkpoint said he and his companions were celebrating Easter in the early-morning hours when unknown men drove up in four vehicles and opened fire, according to the Associated Press.

“We began to shoot back from behind the barricades, and we threw molotov cocktails at them,” Yuri Zhadobin, who coordinates the pro-Russia group, told the AP.

‘Psychological stress’

That the attack occurred during Easter celebrations has shaken Ukrainians.

“After Easter, we have hopes for a political change, an end to this psychological stress,” said Lilya, a 37-year-old accountant visiting the monastery at Nikolskoe.

She said that she favored some kind of federation that would give the region more independence from Kiev but that she didn’t think it should necessarily become a part of Russia.

“It’s all so complicated,” she said, declining to give her last name because of the delicate political situation.

The monastery she was visiting was founded by the monk Zosima, who was said to be a miracle worker and who died in 2002.

Because Zosima had been the confessor and spiritual adviser of Yanukovych, the ousted president, opposition leaders said they suspected that Yanukovych came to hide in the monastery after he was overthrown.

Father Pheophan, the monk in charge of security, said this was not true and was simply another rumor in a country full of rumors.

As he stood beneath rows of icons painted in gold and contemplated the conflict in eastern Ukraine, the monk said, “You look around the countryside, you see lots of monuments from the Second World War? We had a lot of heroes, a lot of fighting. We like to think that nobody can put the people of Donetsk on their knees.”

Alex Ryabchyn in Nikolskoe and Katie Zezima in Washington contributed to this report.