Ukraine said on Tuesday seven of its servicemen had been killed in the past 24 hours as a result of increased attacks by pro-Russian rebels, the highest reported daily casualty figure since August.
International efforts are underway to end a conflict that has contributed to the worst tensions between Moscow and the West since the Cold War. A ceasefire signed in February 2015 has failed to quell all fighting in Ukraine's separatist eastern territory, with each side accusing the other of violations.
Oleksander Turchynov, secretary of Ukraine's National Security and Defense Council, said militants backed by Russia had intensified attacks on government troops using heavy weapons that are meant to have been withdrawn from the frontline under the 'Minsk' peace deal negotiated by Berlin and Paris.
"I want to draw the attention of our strategic partners to the blatant and cynical discrediting by Russia of all the joint peace efforts," he said in statement.
The German government said the leaders of Russia and Ukraine had talked to Chancellor Angela Merkel and the French President on Monday night about preparations to hold elections in the conflict zone of eastern Ukraine.
Progress on implementing the Minsk accords, including the elections and restoration of Ukrainian control over its border with Russia, has stalled.
Russia denies Western charges it has provided the rebels in the Luhansk and Donetsk regions with arms and troops in a conflict that has killed some 9,000 people and led to Western economic sanctions against Moscow.
Government forces shelled the Western outskirts of separatist-held Donetsk city late on Monday, damaging eight residential buildings, separatist news service DAN reported.