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.

Apart from 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.

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.