Violence in eastern Ukraine is intensifying and Russian-backed rebels have moved heavy weaponry back to the front line, international monitors warned on Saturday as Moscow responded by accusing the West of dragging the world back 50 years.

Russian Prime Minister Dmitry Medvedev described East-West relations as having "fallen into a new Cold War" and said NATO was "hostile and closed" towards Russia, in the latest sign that peace efforts have made scant progress almost two years since Moscow annexed Crimea.

"I sometimes wonder — are we in 2016 or 1962?" Medvedev said in a speech to the Munich Security Conference.