The separatist forces in Donetsk say they have established two corridors for the evacuation of civilians from Mariupol, an indication that a large attack on the key Azov Sea port could be imminent.

Eduard Basurin, a spokesman for the separatists’ military, said civilian safety of movement is guaranteed until Wednesday in the corridors.

Mariupol, an industrial centre, is seen as a key target for Russian forces for its economic value and its location.

Its capture would help Russia establish a land corridor between Crimea and the Russian mainland.