Ukrainian officials have said their forces have retaken the airport in the eastern city of Donetsk after launching a counter-attack.

The Kremlin has expressed "concern" at the escalation in fighting, which has put a truce reached in September under pressure.

It comes as thousands of people in Kiev took part in a memorial rally for 12 civilians who died earlier in the week, when their bus came under rocket attack in eastern Ukraine.

This footage, captured on Sunday, shows the remains of Donetsk airport, all but destroyed by the ongoing conflict.