Four Ukrainian servicemen have been killed and another 15 have been injured in the anti-terrorist operation (ATO) zone in the country's eastern regions over the past 24 hours, Ukrainian presidential administration spokesman Andriy Lysenko has said.

"Four of our soldiers have been killed and another 15 have sustained injuries of varying degrees of gravity as a result of fighting in the past 24 hours," he told a press briefing in Kyiv on Monday.