MOSCOW - It is vital that dialogue involving all parties in Ukraine should begin on the basis of ceasefire, Russian President Vladimir Putin said Sunday.

Dialogue should begin on the basis of ceasefire in order to find compromises acceptable for all parties in Ukraine, and "the key to success lies in substantive and meaningful dialogue," Putin said Sunday in a speech to mark the Day of Remembrance of Victims of the Great Patriotic War.

There were "quite active operations of artillery" last night on the Ukrainian side, he said, calling for an immediate stop of hostile actions.

Also on Sunday, Russian Foreign Minister Sergei Lavrov said that without a comprehensive truce and the start of direct talks between Ukrainian authorities and the militia in southeastern regions, it will be impossible to de-escalate the acute crisis in Ukraine.

In a phone conversation with U.S. Secretary of State John Kerry, Lavrov and his U.S. counterpart discussed the situation in Ukraine in the context of a peace plan announced by Ukrainian President Petro Poroshenko.

Poroshenko on Friday announced a week-long ceasefire in the fight against insurgents in the eastern Ukraine. The truce between government forces and insurgents will start at 10:00 p.m. local time (2000 GMT) on June 20 and will end at 10:00 a.m. next Friday, according to Ukraine's presidential press service. (Xinhua)