At least four people were killed today in a gun battle in eastern Ukraine, shattering a fragile Easter truce.

Three pro-Russian militants and one attacker were killed in a firefight at a roadblock close to the separatist-held town of Sloviansk.

A pro-Russian activist at the scene said that around 20 attackers in four cars had opened fire with automatic weapons on the rebel post early today.

The identity of the assailants was not known, but Russia’s Foreign Ministry blamed the attack on Ukrainian nationalists.

It was the first fatal incident in the region since Thursday’s agreement, prompting Sloviansk rebel leader Vyacheslav Ponomarev to call on Russian President Vladimir Putin to send peacekeepers.

The Kiev government had pledged a halt to military operations to oust the rebels until the end of the Orthodox Easter holidays today.

Meanwhile, Orthodox church leaders in Kiev and Moscow traded tirades over the Ukraine crisis as politics overshadowed the traditional Easter observances.

Patriarch Filaret told the faithful in Kiev that Russia was an “enemy” whose “attack” on Ukraine was doomed to failure because it was evil and contrary to God’s will.

Kiev’s politicians echoed their church’s position.

Unelected Prime Minister Arseniy Yatsenyuk lashed out at President Putin, alleging he had a “dream to restore the Soviet Union.”

Outside the country, Kiev’s international backers were also getting involved.

The Washington Post reported that the US was about to deploy ground troops to Poland and possibly the Baltic states to expand the Nato presence in eastern Europe.

Poland’s Defence Minister Tomasz Siemoniak was quoted as saying that his country would be taking a lead role in the operation.

Meanwhile Ukraine’s communists appealed for international solidarity, warning that the Ukrainian secret service was collecting materials about the Communist Party and falsifying party documents with the intention of persuading the Supreme Court to ban the party.

General secretary Petro Symonenko said that the Kiev government “under the guise of fighting for European values was transforming Ukraine into a country with a fascist dictatorship.”

He said Kiev’s position “compromises democracy, freedom of speech and the supremacy of law.”