Bringing peace to the Donbass region was a top campaign pledge for Zelenskiy, helping him to a landslide presidential election victory in April. He strengthened his power base in a parliamentary election last month.

Conflict between Ukrainian troops and Russian-backed forces has killed an estimated 13,000 people since 2014. A ceasefire deal brokered by France and Germany ended major conflict in eastern Ukraine in 2015, though small-scale clashes still occur regularly.

Ukraine's President Volodymyr Zelenskiy on Wednesday pressed Russian leader Vladimir Putin for a resumption of peace talks after four Ukrainian soldiers were killed by shelling in the eastern Donbass border region.

He said that, in a phone call with Putin on Wednesday, he had urged his Russian counterpart to exert influence over the Donbass fighters and agree to relaunch peace talks.

Tuesday's four deaths marked the highest toll of Ukrainian troops in a single day since Zelenskiy took office.

"I said that this doesn't bring us closer to peace," Zelenskiy said of the phone call. "I beg you to influence the other side so that they stop the killing of our people."

He said the Russian president had promised him something, details of which would be disclosed later.

Putin in turn said Ukrainian forces must stop the shelling of settlements in the Donbass that led to civilian casualties.

Both sides agreed to intensify work on prisoner exchanges. Russia holds dozens of Ukrainian captives from the conflict but it is unclear how many Russians are being held in Ukraine.

The leaders of Ukraine, Russia, France and Germany last met in 2016 for their "Normandy Format" talks on the Donbass.

Zelenskiy said he planned to speak to French President Emmanuel Macron and German Chancellor Angela Merkel about arranging more talks. The Kremlin said Putin and Zelenskiy had discussed the prospect of such a meeting.