Ukrainian President Volodymyr Zelenskiy urged the leaders of Russia, Germany and France to resume talks on a peaceful solution to the separatist conflict in Ukraine's eastern Donbass region after four soldiers were killed in shelling Tuesday.
Ukraine's Defense Ministry said this was the highest death toll in a single day since last October. The shelling happened despite a cease-fire agreement reached with Russia-backed separatists last month.
"The cease-fire lasted for 17 days. Today's incident is aimed at undermining not only this truce but also the negotiation process as a whole," Zelenskiy posted on his Facebook account.
Conflict between Ukrainian troops and Russian-backed forces has killed 13,000 people since 2014. The Minsk agreement, involving Russia and Ukraine and brokered by France and Germany, ended major conflict in eastern Ukraine in 2015, although regular small-scale clashes have still cost lives.
The four countries last met in 2016, but a definitive peace has proved elusive with Ukraine and Russia trading blame.
Ukraine says the Kremlin does not want to fulfill its commitments to withdraw military staff and to stop providing separatists with weapons, money and forces. Russia also says that Ukraine is not honoring commitments.
The Minsk agreement states that after a sustained cease-fire is in place the two sides should move toward a peaceful resolution, but one cease-fire after another has been violated.
New President Zelenskiy came to power this year promising to end the conflict and offered talks with Russian President Vladimir Putin in a neutral venue.
"Today the whole world has seen who does not want peace," Zelenskiy said. "That is why I call on ... Emmanuel Macron, Angela Merkel and Vladimir Putin to come together as soon as possible to resume negotiations."