Ukraine's prime minister says two drones have been delivered to the country so international observers can monitor the shaky cease-fire between government forces and pro-Russian separatists in eastern Ukraine.

Prime Minister Arseniy Yatsenyuk said Monday the drones will be given to the Organization for Security and Cooperation in Europe after they are cleared by customs.

The Sept. 5 cease-fire has been routinely violated. The government-controlled airport in the biggest rebel-held city, Donetsk, is a key flashpoint and residential neighborhoods nearby are frequently hit by artillery crossfire.

Yatsenyuk says Russia is doing nothing to mitigate the hostilities. He accuses Moscow of stationing troops in Ukraine — a claim Russia has denied.

Russian Foreign Minister Sergey Lavrov urged all to uphold the truce and warned against blaming all violations on rebels.