DONETSK, Ukraine (Reuters) - A Russian-backed leader in the breakaway Donetsk region of Ukraine said on Wednesday that a military mobilisation was gathering pace to counter Ukrainian "aggression".

       Denis Pushilin, leader of the self-proclaimed Donetsk People's Republic that was recognised by Russia this week, said the situation had become critical but the separatists would win with support from "big Russia".

       (Reporting by Polina Nikolskaya; Writing by Mark Trevelyan; Editing by Alex Richardson)