SLAVYANSK, Ukraine - Four people were reported killed Sunday in a gun battle in restive eastern Ukraine, shattering a fragile Easter truce in the crisis-hit former Soviet republic.
Three pro-Russian militants and one attacker were killed in a deadly firefight at a road block close to the separatist-held town of Slavyansk, local leader Vyatcheslav Ponomarev said.
The identity of the assailants was not known. Kiev's interim government had pledged a halt to military operations to oust the rebels until the end of the Orthodox Easter holidays on Monday.
A pro-Russian militant at the scene told AFP that roughly twenty attackers in four cars had opened fire with automatic weapons on the rebel post early Sunday. He could not, however, confirm any casualties.
The reported violence came as the United States was pressing Russia to persuade the pro-Kremlin rebels to abide by an international accord calling for them to surrender their weapons and leave occupied public buildings.
Overnight, Orthodox leaders in Kiev and Moscow traded barbs over the Ukraine crisis as politics overshadowed traditional Easter observances.
Patriarch Filaret thundered to the faithful in pro-West Kiev that Russia was an "enemy" whose "attack" on Ukraine was doomed to failure because it was evil and contrary to God's will.
In Moscow, the patriarch of the Russian Church, Kirill, delivered a prayer for Ukraine in which he called on God in turn to put "an end to the designs of those who want to destroy Holy Russia".
Kirill said that while Ukraine was "politically" separate, "spiritually and historically" it was at one with Russia, and he prayed that it would benefit from authorities that are "legitimately elected".
In comments to be broadcast on US television Sunday, Ukrainian Prime Minister Arseniy Yatsenyuk lashed out at Russian President Vladimir Putin - whom Kiev and Washington accuse of masterminding the insurgency in Ukraine - for having a "dream to restore the Soviet Union".
Yatsenyuk, speaking to NBC's "Meet the Press", also condemned those who reportedly handed out pamphlets demanding Jews register or be expelled in the east of Ukraine as "these bastards" who should be brought to justice.
The United States on Saturday was reported to be flexing its military muscle in a warning to Russia, which has tens of thousands of troops massed on Ukraine's border.
The Washington Post said that the US was about to deploy ground troops to Poland and maybe Baltic states to expand NATO's presence in eastern Europe.
Poland's defence minister, Tomasz Siemoniak, was quoted saying that Poland, a NATO member, would be taking a lead role in the operation.
Washington has warned Moscow that Ukraine is in a "pivotal period" as the pro-Russian rebels refuse to comply with the Geneva accord reached Thursday by Russia, the US, Ukraine and the EU to disarm.
US Secretary of State John Kerry told Russian Foreign Minister Sergei Lavrov that "full and immediate compliance" was needed within "the next few days".
The Kremlin has snapped back by stressing its troops' deployment on Ukraine's doorstep - an apparent warning that the situation could rapidly deteriorate if Washington follows through with a threat to impose further sanctions.