Ukraine's army on Wednesday accused pro-Russian forces of launching a big new attack against government positions in breach of a shaky ceasefire deal.

Rebel forces began a "large-scale offensive against Ukrainian positions" close to the seperatist stronghold of Donetsk at 0400 local time (0100 GMT) using some dozen tanks and up to a thousand troops, Ukraine's General Staff said in statement, adding that government troops had fought back the attack using heavy artillery.