Pro-Kremlin rebels in east Ukraine appealed Sunday forhelp from Russian "peacekeepers" after a deadly gunfight killed at least two of theirmilitants, shattering an Easter truce and sparking "outrage" in Moscow. But the Western-backed authorities in Kiev claimed the violence was a set-up byRussia to create a pretext for it to send in troops.The attack, near the flashpoint town of Slavyansk, undermined an accord workedout in Geneva between Russia, Ukraine and Western powers on Thursday underwhich "illegal armed groups" were to surrender their weapons.The deal, aimed at easing what has become the worst crisis between Russia and theWest since the Cold War, now appears to have stalled.Russia has an estimated 40,000 troops massed on Ukraine's border in what NATOsays is a state of readiness to invade, while the United States, according to TheWashington Post, is preparing to send ground troops to neighbouring Poland.Vladimir, a masked 20-year-old pro-Russian rebel, said Sunday's shootout eruptedwhen four cars pulled up to a roadblock manned by the separatists in the earlymorning hours."We wanted to conduct a check, and then they opened fire on us with automaticweapons," he said.Three of the separatists were killed, he said.An AFP photographer saw two bodies laid out in a truck near the scene.The identity of the assailants, who escaped before the pro-Russian rebels couldbring in reinforcements, was not known.The leader of the separatists in Slavyansk, Vyacheslav Ponomaryov, said he believedtwo attackers were also killed.He declared a midnight-to-6:00 am curfew in Slavyansk, and appealed for RussianPresident Vladimir Putin to send in troops as "peacekeepers to defend thepopulation against the fascists" -- the separatists' label for Ukraine's newgovernment and its supporters.Later, Ponomaryov said: "If you can't send peacekeeping forces, send us weapons."- Moscow blames ultra-nationalists -Putin has said he "very much hopes" he will not have to send his forces into Ukraine,but asserts he has a "right" to do so.On Sunday, Russia's foreign ministry declared its "outrage" at the deadly attack.It blamed the deaths of the "innocent civilians" on ultra-nationalists who were at thevanguard of the street protests that forced the February ouster of Ukraine's pro-Kremlin president Viktor Yanukovych.The ministry said locals had found the attackers' cars containing weapons, satellitemaps and business cards belonging to the ultra-nationalist group Pravy Sektor("Right Sector"). It demanded the Ukrainian government abide by the Geneva accord.But a Right Sector spokesman told AFP that Russia's claims were "lies" and"propaganda" designed to portray the east as ungovernable for Kiev.Ukraine's government, confirming three people were killed, described the latestviolence as a "cynical provocation" by Russian-armed separatists.Interior Minister Arsen Avakov, who travelled to the east on Sunday to inspecttroops in the region, said investigations were ongoing into the shootout.- Geneva accord stalled -The gunfight ended days of relative calm underpinned by a promise by theWestern-backed authorities in Kiev to suspend military operations to oust the rebelsover Easter.The last deadly clash was on Thursday, when three pro-Russian militants were killedby Ukrainian soldiers when they tried to attack a military base in the southeast portcity of Mariupol.But with the pro-Kremlin rebels refusing to comply with the Geneva accord,Washington has been ratcheting up pressure on Moscow, which it sees as pulling thestrings in the Ukrainian insurgency.US President Barack Obama has threatened to impose more sanctions on Moscow ifno progress is made on the ground.A Kremlin spokesman shrugged off as "absurd" claims that Washington couldsanction Putin directly, after an article in Britain's The Times newspaper citedanonymous sources saying the United States could target Swiss bank accountsbelonging to the leader that allegedly hold some $40 billion (29 billion euros).Russia's ambassador to the United States, Sergei Kislyak, told Fox News thatsanctions represented a return to the "Cold War mentality" but said Moscow could"withstand pressures".- Prayers for peace -Pope Francis pleaded for peace in Ukraine in his Sunday Easter prayer. "We ask youto enlighten and inspire the initiatives that promote peace in Ukraine," he prayed.But efforts to that end were undermined overnight when the Orthodox Christianleaders in Kiev and Moscow traded barbs.Kiev's Patriarch Filaret thundered that Russia was an "enemy" whose "attack" onUkraine was doomed to failure because it was evil and against God's will.In Moscow, the patriarch of the Russian Church, Kirill, led a prayer calling on God toput "an end to the designs of those who want to destroy Holy Russia" and pleadingfor Ukraine to soon have "legitimately elected" leaders.In comments broadcast on US television on Sunday, Ukrainian Prime MinisterArseniy Yatsenyuk lashed out at Putin for having a "dream to restore the SovietUnion"."The world has a reason to be concerned about Putin's intention because what (the)Russia Federation did, they undermined the global stability," Yatsenyuk told NBC's"Meet the Press".Washington has warned Moscow that Ukraine is in a "pivotal period" and saidprogress was needed on the Geneva accord "within days".US Vice President Joe Biden is scheduled to make a visit to Kiev on Tuesday.