UPDATE 1-Ukraine's Zelenskiy says called Putin after 4 soldiers killed

Ukraine's President Volodymyr Zelenskiy said he had a phone conversation with Russian leader Vladimir Putin on Wednesday morning after four Ukrainian soldiers were killed by shelling in the eastern Donbass region.

Zelenskiy called on Putin to exert influence over the Donbass fighters. He also said Putin had promised him something, details of which would be disclosed later. "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."

The Kremlin has not commented on the phone call. The conflict between Ukrainian troops and Russian-backed forces has killed 13,000 people since 2014. A ceasefire agreement, involving Russia and Ukraine and brokered by France and Germany, ended the major conflict in eastern Ukraine in 2015, although regular small-scale clashes have still cost lives.

The four soldiers' deaths -- the highest toll in a single day since October -- prompted Zelenskiy to urge the resumption of talks for a peaceful solution to the conflict. The leaders of the four countries last met in 2016. Ukraine accuses Russia of waging an undeclared war against Kyiv in the Donbass, supplying troops and heavy weapons to the region, which Moscow denies.

Russia says Ukraine is not honouring commitments under the ceasefire agreement brokered in Minsk in 2015.