The foreign ministers of Russia, Ukraine, France and Germany early Tuesday called for an immediate stop to resurgent combat operations in eastern Ukraine.

The joint declaration, issued after four hours of at-times hefty discussions, called for a stronger role for the observer mission of the Organization for Security and Cooperation in Europe (OSCE) and for the withdrawal of heavy weapons, (dpa) news agency reported.

The ministers also called for formation of the long-planned work groups including the parties to the conflict and the Organization for Security and Cooperation in Europe (OSCE) to formulate a concrete political solution.

The meeting was the fifth round in Berlin in recent months to review progress made in implementing the Ukraine peace deal reached some two months ago.

German Foreign Minister Frank-Walter Steinmeier, who released the joint declaration early Tuesday, indicated that some of the discussions were very contentious.

"Everyone knows that we still have a long way ahead of us," he said.

The ministers discussed improving humanitarian supply lines into contested areas, restarting prisoner exchanges and preparing for the local elections that were agreed to under the deal signed in Belarus.