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MOSCOW, June 21 (Reuters) - Russian President Vladimir Putin said on Saturday he supported Ukraine's ceasefire, but added that without "practical action" to start negotiations the plan would not be viable.
"Vladimir Putin supports the decision of the President of Ukraine Petro Poroshenko to cease fire in the southeast of Ukraine, as well his stated intentions to take a number of concrete steps to achieve a peaceful settlement," the Kremlin said in a statement.
"However, the Russian head of state drew attention to the fact that the proposed plan, without practical action aimed at the beginning of the negotiation process, will not be viable and realistic."
The Ukrainian forces' seven-day ceasefire began at 10 p.m. on Friday, as part of the president's plan to end a rebel insurgency in the east of the country.
On Saturday, pro-Russian separatists attacked Ukrainian posts on the border with Russia and a military base and tried to storm an airforce base overnight into Saturday, government forces said..
The Kremlin said, without referring to any of the sides involved in the conflict, that Putin considers unacceptable that after the ceasefire order there were sounds of explosions and ammunition reaching Russian territory from Ukraine.
He also said the peace plan should not be an ultimatum to the militias.
"The opportunity which opens with the ceasefire should be used to start meaningful negotiations and political compromise between the opposing sides in eastern Ukraine," the Kremlin cited Putin as saying.
"The Russian president calls on all parties to the conflict to cease fire and sit down at the negotiation table." (Reporting by Lidia Kelly; Editing by Alison Williams)