Pro-Russian separatists had reinforced their position with tanks and missile systems in East Ukraine.

As the talks in Minsk dragged on through Wednesday night, around 50 tanks, 40 missile systems and 40 armoured vehicles entered east Ukraine's breakaway Luhansk region from Russia via the Izvaryne border crossing, Ukrainian military spokesman Andriy Lysenko said.

Pro-Russian separatists have strengthened their positions especially in Debaltseve, a strategic transport hub that has been the focus of heavy fighting in recent weeks, Lysenko said, stressing that government forces had not given up any ground.

But Pro-Russian separatists senior commander Eduard Basurin said separatist forces had completely encircled Ukrainian troops in the town and their only option was to surrender. He said his side would honour the Minsk agreements.

According Ukrainian armed forces, 1,500 Russian troops and convoys of military hardware entered Ukraine over the weekend.

“One thousand five hundred Russian soldiers and 300 pieces of military equipment, including BM-21 Grad missile systems, crossed the Ukraine-Russia border on February 7 and 8,” Ukraine military spokesman Andriy Lysensko told journalists.