Russian President Vladimir Putin on Monday declared a three-day ceasefire in the war with Ukraine next month to mark the 80th anniversary of the victory of the Soviet Union and its allies in World War Two.

The Kremlin said the 72-hour ceasefire would run from the start of May 8 to the end of May 10, and Russia called on Ukraine to join it as well.

In the event of violations by the Ukrainian side, Russia's armed forces would give an "adequate and effective response," the statement said.