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.

In addition to the 479 drones, 20 missiles of various types were fired at different parts of Ukraine from Sunday to Monday, according to the air force, which said the barrage targeted mainly central and western areas.

The warring sides also exchanged prisoners in one of the few results of talks last week, and Russia reported new attacks on the front line.