Ukraine's President Petro Poroshenko on Tuesday demanded a "tough reaction" from the West against Russia over a broken ceasefire deal in a phone call with German Chancellor Angela Merkel, his office said.

Poroshenko labelled fierce fighting in the key town of Debaltseve a "cynical attack" on the European-brokered truce and called for a "tough reaction against the treacherous actions of the rebels and Russia" from the European Union and the international community.