Russian President Vladimir Putin said that Moscow hoped for more peace talks with Ukraine but that the momentum of the war was in its favour, signalling no shift in his stance despite a looming sanctions deadline from Washington.

The move means Trump is walking back the 50-day deadline he set this month in response to Russia's continued bombing of Ukrainian cities.

A Russian airstrike on a prison in southeastern Ukraine killed at least 17 inmates and wounded more than 80 others, officials said.