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.

As well as 479 drones, 20 missiles of various types were fired at different parts of Ukraine, according to the air force, which said the barrage targeted mainly central and western areas of Ukraine.

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.