Russia and Ukraine exchanged prisoners of war under the age of 25 on Monday in emotional homecoming scenes, the first step in a series of planned prisoner swaps that could become the biggest of the war so far.

Russian officials said Sunday that Moscow is still awaiting confirmation from Kyiv on a planned exchange of 6,000 bodies of soldiers killed in action, accusing Ukraine of delaying the process.

The Russian Defense Ministry announced on Monday that Moscow and Kyiv had exchanged the first group of servicemen under the age of 25 in the first round of a large-scale swap carried out under an agreement reached in Istanbul last week.