NATO Secretary General Jens Stoltenberg has urged Russia to stop its support for the separatists in the eastern Ukraine immediately, to stop destabilizing Ukraine and to respect its international commitments.

"In recent weeks, Russia has supplied hundreds of pieces of advanced equipment, including rocket systems, heavy artillery, tanks, armored vehicles and electronic warfare systems. We call on Russia to stop its support for the separatists immediately, to stop destabilizing Ukraine and to respect its international commitments," he said at a briefing at the NATO headquarters in Brussels on Monday.

Besides, Stoltenberg condemned the sharp escalation of violence along the ceasefire line in eastern Ukraine, in the town of Mariupol, by Russia-backed separatists.

"The aggressive actions and provocative statements of the separatists are in direct contradiction with the Minsk agreements," he stressed.

The Secretary General has said that such indiscriminate attacks are unjustified and unacceptable.

"This comes at great human cost to civilians. We express our condolences to the Ukrainian people for these tragic losses. Thirty civilians were killed and around a hundred were injured in the attack launched on residential areas of Mariupol," he said.