Updated

Russian Foreign Minister Sergey Lavrov has vowed to use Moscow's influence to get Ukraine's separatist rebels to comply with a cease-fire deal.

Lavrov made the promise at a news conference Monday with EU foreign policy chief Federica Mogherini after talks in Moscow.

An American member of the Organization for Cooperation and Security in Europe's monitoring mission was killed and two others wounded Sunday in eastern Ukraine's separatist-controlled Luhansk region when their vehicle hit a mine.

The U.S. State Department has called on Russia to use its influence on the rebels to improve security in eastern Ukraine.

Both the Russia-backed rebels and the Ukrainian government blamed each other for laying the mine. Fighting in eastern Ukraine has killed more than 9,900 people since it began in 2014.