Russia and Ukraine began a major prisoner exchange, swapping hundreds of soldiers and civilians in the first phase of an exchange that was a moment of cooperation in otherwise failed efforts to reach a ceasefire in the 3-year-old war.

Russia and Ukraine have completed the first phase of what is expected to be the biggest prisoner exchange since the start of the war, with almost 800 people released on Friday.

The agreement to exchange 1,000 prisoners each was the only concrete step toward peace to emerge last week from direct talks.