Ukraine claimed it had regained control of swathes of the separatist east today even as Washington expressed concern over the appearance of fighters from Russia's war-ravaged region of Chechnya among the insurgents.
The rebels for their part dismissed speculation of a rift in their ranks after a dozen local militants were evicted from their seat of power in Donetsk by a military brigade comprised largely of Chechens and other Russians from the volatile North Caucasus.
Both Kiev and its Western allies have long accused the Kremlin of choreographing a seven-week insurgency that has shaken Ukraine's foundations -- a charge that Russian President Vladimir Putin denies.
But the recent appearance among the separatists of trained gunmen from Chechnya -- a mostly Muslim region that fell under Kremlin control following two post-Soviet wars for independence -- has fuelled fears of the conflict being transformed into a proxy war involving elements from other unstable regions of the former Soviet Union.
Ukraine's acting defence minister said his forces were in high spirits despite the downing of a military helicopter yesterday by the rebels that killed 11 soldiers and a general.
"Our armed forces have completed their assigned missions and completely cleared the southern and western parts of the Donetsk region and the northern part of the Lugansk region from the separatists," Mykhailo Koval told reporters.
Pro-Russian militants seized about a dozen towns and cities in the two eastern industrial regions in response to the popular ouster in Kiev of a Kremlin-backed president.
Rebels in control of the Lugansk and Donetsk government buildings have declared independence and are seeking a merger with Russia similar to that accomplished by Ukraine's Black Sea peninsula of Crimea following its seizure by pro-Kremlin troops in March.
Ukraine's acting defence chief said his soldiers intended to push ahead with their so-called "anti-terrorist operation" despite demands by Moscow for all military activities to come to an immediate halt.
"We will continue working until this region starts working and leading a normal life," said Koval.
Ukraine's acting president Petro Poroshenko also vowed to punish those who used a sophisticated surface-to-air missile to shoot the MI-8 helicopter out of the Lugansk sky.
"We have to do everything we can to ensure no more Ukrainians die at the hands of terrorists and bandits. These criminal acts by the enemies of the Ukrainian people will not go unpunished," Poroshenko told Ukrainian news agencies.
US Secretary of State John Kerry said he was encouraged by signs that Russia was pulling its troops back from Ukraine's eastern border.
But he said the appearance of Chechens in Donetsk and Lugansk was a dangerous new development that Putin should quickly address.
