Russian-backed rebels massing to attack key Ukrainian towns - Kiev

A member of a rebel unit of the self-proclaimed separatist Donetsk People's Republic walks past a house destroyed by shelling in the village of Olenivka, south of Donetsk, February 7, 2015. REUTERS/Maxim Shemetov

DONETSK, Ukraine (Reuters) - Pro-Russian separatists have intensified shelling of government forces on all front lines and appear to be amassing forces for new offensives on the key railway town of Debaltseve and the coastal city of Mariupol, Ukraine's military said on Saturday.

Five Ukrainian soldiers have been killed and 26 wounded in fighting in the past 24 hours, spokesman Volodymyr Polyovy told a briefing in Kiev.