Russia and Ukraine carried out a rare prisoner swap Monday involving captives under 25, marking the first in a series of planned exchanges that could become the largest of the war, as emotional reunions unfolded on both sides.

The exchange was the result of direct talks between the two sides in Istanbul on June 2 that resulted in an agreement to exchange at least 1,200 POWs on each side and to repatriate thousands of bodies of those killed in Russia's war in Ukraine.

The return of POWs and the repatriation of the bodies of the dead is one of the few things the two sides have managed to agree on as broader negotiations have failed to get close to ending the war, now in its fourth year.

Fighting has raged on, with Russia saying Monday its forces had taken control of more territory in Ukraine's east-central region of Dnipropetrovsk and Kyiv saying Moscow had launched its largest drone attack of the war.

Officials in Kyiv said some of the Ukrainian prisoners who came home Monday had been in Russian captivity since the beginning of the war.