Ukraine president warns of attack
Ukrainian President Petro Poroshenko has warned of a possible large-scale offensive by separatist forces in the east.
The concerns come a day after a major battle erupted on the western edge of the main separatist rebel stronghold.
Hostilities on Wednesday left more than a dozen dead and brought a February cease-fire agreement between Russia-backed rebels and government troops to breaking point.
In his annual address at Parliament on Thursday, Mr Poroshenko spoke of a "colossal threat of the resumption of large-scale hostilities by Russian and terrorist forces" and said there are 9,000 Russian troops in the rebel-controlled area right now.
Russia has strongly denied supplying the rebels either with weapons or with recruits, despite mounting evidence suggesting otherwise.