Russian President Vladimir Putin has called on militants in east Ukraine to open a humanitarian corridor for surrounded Ukrainian troops, the Kremlin's press service said in a statement in the early hours of Friday.

"I call on the militant forces to open a humanitarian corridor for the Ukrainian troops who have been surrounded, in order to avoid senseless casualties and let them freely withdraw from the area of military operations and reunite with their families, return to their mothers, wives and children, and immediately provide medial aid to those wounded in the military operation, " the statement says.