Ukrainian President Petro Poroshenko has called for UN peacekeepers to be deployed to Eastern Ukraine to enforce a ceasefire.

At an emergency security meeting, he said such a force would help guarantee security "in a situation where the promise of peace is not being kept".

His comments came after Ukrainian troops withdrew from the strategic city of Debaltseve after intense fighting.

The rebel advance on Debaltseve, which came in spite of the ceasefire agreed last week, has recieved international condemnation.

Poroshenko`s request was approved by Ukraine`s national security and defence council at the emergency meeting on Wednesday night.

Amendments to Martial Law elaborated as pursuant to the instruction of the President will be introduced to the Rada in several days.

Poroshenko said almost 2,500 Ukrainian soldiers had withdrawn from Debaltseve on Wednesday. He said the withdrawal had been organised, but that at least six soldiers were killed and more than 100 wounded.