A new prisoner swap between Ukraine and Russia has begun, officials in both countries said Monday, with Ukrainian soldiers who have spent nearly the entire duration of the war in captivity among those returning home.

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.

Ukraine's president says a new prisoner exchange with Russia is ongoing and will take days, as both sides continue launching hundreds of attack drones.