Ukraine's Easter ceasefire has been shattered after at least three people were killed in a checkpoint shootout, leaving the Geneva peace deal in tatters.
Moscow and Kiev both accused one another of complicity in yesterday's attack, which threatens to torpedo tentative attempts to negotiate a peaceful outcome to the crisis in eastern Ukraine.
The gunfight in Bylbasovka, a village on the outskirts of the separatist-controlled town of Slavyansk, broke out just four days after the EU and the Ukrainian, Russian and American governments signed a "de-escalation" deal in Geneva designed to find a peaceful solution to the crisis.
According to the Ukrainian interior ministry, fighting began when unidentified men in four vehicles opened fire at a checkpoint manned by pro-Russian activists at about 2am yesterday morning, killing at least three people.
The activists returned fire, destroying two cars and injuring and killing an unknown number of attackers, the statement said.
About 12 attackers were believed to have escaped with their dead and wounded in their two remaining vehicles, though the ministry said it did not know how many of them were hurt.
Russian state media reported five people had died. Ukrainian police have launched a murder inquiry.
While it seems clear that a fight did take place, and several people were killed, further accounts of the fight are confused.
"They drove right up to the barricade and started shooting from the vehicles," said one man who declined to give his name. "Those who could get away did so. But they killed my friend. He was 22."
The man, who was visibly distraught, said the activists manning the checkpoint were peaceful protesters armed only with sticks. "They promised a ceasefire for today, and then they do this. Why?" he said.
Other locals said the position had been surrounded by snipers in black camouflage before pro-Russian "self-defence" units from Slavyansk arrived to return fire.
There were two burnt-out vehicles at the scene in front of a tyre barricade, typical of the checkpoints that have been erected by pro-Russian groups across the region.
Bullet holes in the rear vehicle appeared to have been fired from close to the ground from a position to its rear and left – the other direction from the barricade.
It was unclear if anyone had been in the vehicle at the time it was shot or caught fire, but there was no sign of blood in the vehicle or on the road.
The cars appeared to have been moved since they caught fire, with residue from burnt tires and glass from what appeared to be shattered rear lights found closer to the barricade. A number of Molotov cocktails were lined up ready for use behind the barricade, although it was unclear whether any had been used in the fight.
Both Russia and the separatist militia in control of Slavyansk have blamed the attack on Right Sector, a far-right militia group that was prominent in the February revolution in Kiev.
"Innocent civilians were killed as a result of an armed attack by militants from the so-called 'Right Sector'," the Russian foreign ministry said in a statement.
"The Russian side is angered by this provocation by militants, which testifies to the reluctance of the authorities in Kiev to curb and disarm nationalists and militants," the statement said.
Ukrainian authorities in turn accused Russian-backed "external provocateurs" of staging the attack as part of a "cynical provocation".
"There was no organisation in Slavyansk other than the saboteurs and criminals who are supported and armed by officers of the GRU, Russia's military intelligence agency," said Ukraine's state intelligence agency in statement.
"False information presented in some Russian media has been unambiguously refuted by investigators who are investigating the crime," the statement read.
'LifeNews', a pro-Kremlin Russian tabloid, earlier published a video of evidence supposedly captured from the attackers including US dollar bills, a World War II-era machine gun, and the business card of Dmytro Yarosh, the head of Right Sector.
Vyacheslav Ponomarev, the head of the Slavyansk separatists, said the evidence had been taken from the body of one of the attackers, adding that his men had earlier caught other Right Sector activists elsewhere and had them in custody.
Right Sector denied involvement in the killings. "It is a blasphemous provocation from Russia, blasphemous because it took place on a holy night for Christians, on Easter night. This was clearly carried out by Russian special forces," Artem Skoropadsky, a spokesman for the Right Sector, told Reuters.
Pro-Russian gunmen could be seen manning sandbag gun emplacements and positioning captured Ukrainian army vehicles in Slavyansk town centre yesterday afternoon.
The town of 119,000 people 55 miles north of Donetsk is fully controlled by heavily armed separatists who have established checkpoints and barricades at every entrance to the city.
Following the shooting, the pro-Russian activists in control of the town yesterday announced a curfew between midnight and 6am and appealed to Russia to send "peacekeeping troops" to prevent further "provocations". Mr Ponomarev, the self-declared "people's mayor" of Slavyansk, said he wanted Russia to send weapons, food and medicine if it was unable to send troops.
"So far I am only appealing through the media. We have no direct links (with Moscow)," he said at a hastily called press conference.
Although he said he favoured a peaceful solution, he ruled out any negotiations with the Kiev government, calling it an "illegitimate junta". "We are not the aggressors, they are. We're on our own land. We're not sending people to Kiev or Lviv," he said.
Asked how he thought the situation could be resolved peacefully without negotiation, he said "maybe Russia will help us". ( © Daily Telegraph, London)