KIEV, May 24 - 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 under way 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militants backed by Russia had intensified attacks on government troops using heavy weapons that are meant to have been withdrawn from the frontline under the 'Minsk' peace deal negotiated by Berlin and Paris.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.

Ukraine called on Russia early Tuesday to stop massive supplies of lethal weapons to separatist enclaves and to withdraw its troops from the territory.

President Petro Poroshenko, Russian President Vladimir Putin and leaders of France and Germany have spoken by telephone as fighting has escalated in parts of Donbas controlled by pro-Russian separatists.

Russia keeps about 7,000 of its troops in parts of Donetsk and Luhansk reinforcing about 25,000-strong army of the separatist enclaves that mostly consists of Russian mercenaries, according to Ukrainian military intelligence.

Russia recently increased supplies of lethal weapons and ammunitions by railroad to the key separatist strongholds of Debaltseve and Ilovaysk, the intelligence agency reported.

Russia persistently denies presence of its troops in Ukraine, and says it only supplies humanitarian aid to the enclaves.

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. (rt/nr/ez)