The Kremlin said on Tuesday that Russian forces still planned to cease fire in Ukraine from May 8-10 as per President Vladimir Putin's orders, but would respond if Ukrainian forces tried to strike Russian positions.

Putin on April 28 declared a three-day ceasefire to mark the 80th anniversary of the victory of the Soviet Union and its allies over Nazi Germany in World War Two.

The Kremlin said the 72-hour ceasefire would run on May 8, May 9 — when Putin will host international leaders on Moscow's Red Square, including Chinese President Xi Jinping — and May 10.

Ukrainian President Volodymyr Zelenskyy has so far appeared to rule out such a brief ceasefire, saying he is only ready to sign up to a ceasefire that would last at least 30 days, an idea Putin has said needs a lot of work before it could become a reality.

Asked what Russia would do if Zelenskyy did not sign up to the three-day ceasefire, Kremlin spokesman Dmitry Peskov said: "Of course, President Putin's initiative on a temporary ceasefire for the public holidays is valid, and relevant instructions have been given (to the military) by the supreme commander-in-cChief."

"There will be a ceasefire, but in the event that there is no reciprocity on the part of the Kyiv regime and attempts to strike our positions or our facilities continue, then an appropriate response will be given immediately."

Peskov said that Kyiv had not yet given any indication it was ready to sign up to the proposed ceasefire.