Russia and Ukraine have swapped hundreds more prisoners of war, the third and last part of a major swap, hours after a massive attack by Moscow, killing at least 12.

Russia carried out its largest aerial attack on Ukraine, shattering any hopes that a record prisoner exchange completed on Sunday could lead to a cessation of hostilities.

The massive missile and drone attack across Ukraine followed large strikes the night before, and casts more doubt on the U.S.-brokered peace process.