Dmity Peskov, the Russian presidential spokesman.
The Russian Foreign Ministry has called on Western powers to give up their "destructive" policy on Ukraine and urged Kiev to stop its "punitive operation" in the country's south-east, where Ukrainian forces on Friday attempted to retake the separatist-held town of Slovyansk.
"This will allow a real process of de-escalation to begin," the ministry said in a statement, adding the West was effectively preventing a peaceful resolution to the Ukraine crisis by backing the Kiev authorities.
Pro-Russian rebels shot down two Ukrainian helicopters on Friday, killing two crew members, as Ukrainian troops tightened their siege of Slovyansk.
However Dmitry Peskov, the Russian presidential spokesman, said the "punitive operation" mounted by Ukrainian forces had destroyed a peace plan agreed with Western powers two weeks ago.
"While Russia is making efforts to de-escalate and settle the conflict, the Kiev regime has turned to firing on civilian towns with military aircraft and has begun a punitive operation, effectively destroying the last hope of survival for the Geneva accord," he said, referring to a deal signed on April 17 by Russia, Ukraine, the U.S.and the European Union.
Under that agreement, separatists were supposed to lay down their arms and vacate the public buildings they have seized in about a dozen towns they have seized across the Russian-speaking east.
However, since the accord was signed, Pro-Russian separatists have tightened their grip in eastern Ukraine.
Two Dead as Ukraine Forces Try to Retake Slovyansk