Foreign ministers from Russia, Ukraine, Germany and France called for more heavy weaponry to be withdrawn from the front lines in eastern Ukraine, amid recent flare-ups in violence between government forces and Russia-backed rebels.

After a late-night meeting Monday in Berlin, the ministers released a statement saying the situation “remains tense because of numerous cease-fire violations.” It called for the withdrawal of more tanks and heavy weapons by all sides, and more rigorous monitoring of the truce by international observers....