Russia said Sunday that trains carrying more bodies of Ukrainian soldiers were due to depart towards the Ukrainian border, escalating a spat with Kyiv over a prisoner of war swap.

Ukraine and Russia, earlier this month, agreed to exchange 1,000 prisoners of war and civilian detainees each in a rare moment of cooperation in more than three years of war.

MOSCOW/KYIV — A large-scale prisoner exchange between Russia and Ukraine — the only concrete outcome of peace talks — was thrown into doubt on Saturday after Moscow and Kyiv accused each other of delaying and thwarting the swap.