Ukraine on Friday blamed Moscow for shelling a convoy of civilian cars in the southern Zaporizhzhia region that killed at least 23 on the front line.
Zaporizhzhia regional governor Oleksandr Starukh said the strikes had also injured 28 people, "all civilians, local people."
A pro-Kremlin official in Russian-occupied region of Zaporizhzhia blamed Kyiv and denied the Russian army was behind the attack.
"The regime in Kyiv is trying to portray what happened as shelling by Russian troops, resorting to a heinous provocation," Vladimir Rogov said on social media, accusing Ukrainian troops of carrying out a "terrorist act".
The Zaporizhzhia governor said Russian forces "launched a rocket attack on a civilian humanitarian convoy on the way out of the regional centre".
"People were standing in line to leave for the temporarily occupied territory, to pick up their relatives and to take away aid," he said on social media.
Governor Starukh also posted a photograph, showing two rows of crumpled cars and several corpses lying nearby.
The industrial hub of Zaporizhzhia, with a pre-war population of 700,000, is under Ukrainian control but subject to Russian rocket attacks.
Part of the region is occupied by Moscow and the Kremlin has said it plans to formally annex the region at a ceremony in Moscow on Friday.
Separately, a Moscow-installed official in Kherson, a southern Ukrainian region controlled by Russia, was killed in strikes by Kyiv's forces, Russia's state-run news agency cited local officials as saying Friday.
"[Alexei] Katerinichev died as a result of a pinpoint strike from Himars. Two rockets hit the house in which he was," Kirill Stremousov, the deputy head of the Moscow-controlled region, said, referring to the US-supplied weapons systems.