A Ukrainian counter-attack has forced Russian troops into a rapid retreat in the Kharkiv region

Russians retreat in the east

Ukrainian troops have inflicted a "major operational defeat" on Russian forces, according to the Institute for the Study of War (ISW).

Russia confirmed it had withdrawn from the key towns of Izyum and Kupiansk on Saturday, saying that the retreat would allow its troops to "regroup".

Both towns were major logistical hubs for Russian forces in Donbas. Russian troops had been trying to advance towards Kramatorsk and Slovyansk.

Izyum in particular was one of the most fortified sections of the Russian front line.

Ukraine said it had retaken more than 3,000 sq km (1,158 sq miles) from Russian forces.