Apparent Ukrainian shelling on a market in Russian-occupied Donetsk killed at least 25 people Sunday, local officials reported.
Some 20 others, including two children, were injured in the strike on the suburb of Tekstilshchik, said Denis Pushilin, head of the Russian-installed authorities in Donetsk.
He added that the shells had been fired by the Ukrainian military.
Kyiv has not commented on the event and the claims could not be independently verified by The Associated Press.
Emergency services continue to work on the scene, Pushilin said.
Both Moscow and Kyiv have exchanged accusations over airstrikes against each other that intensified in late December when at least 40 people were killed in various regions of Ukraine in a massive air attack, which President Volodymyr Zelenskyy described as the "heaviest attack" since the start of the Russia-Ukraine war.
On Jan. 1, Russian President Vladimir Putin said his country would not let "a single crime of this kind" go unpunished following a subsequent raid on the Russian city of Belgorod, which killed 25 people and wounded many others.
Also Sunday, fire broke out at a chemical transport terminal at Russia's Ust-Luga port following two explosions, regional officials said.
Local media reported that the port had been attacked by Ukrainian drones, causing a gas tank to explode.
The blaze was at a site run by Russia's second-largest natural gas producer, Novatek, 165 kilometers southwest of St. Petersburg.
In a press statement to Russian media outlet RBC, the company said that the fire was the result of an "external influence." It also said that it had paused operations at the port.
Yuri Zapalatsky, the head of Russia's Kingisepp district, where the port is based, said in a statement that there were no casualties, but that the area had been placed on high alert.
News outlet Fontanka reported that two drones had been detected flying toward St. Petersburg Sunday morning, but that they were redirected toward the Kingisepp district. The Associated Press could not independently verify the reports.
The Russian Ministry of Defense did not report any drone activity in the Kingisepp area in its daily briefing. It said that four Ukrainian drones had been downed in Russia's Smolensk region, and that two more had been shot down in the Oryol and Tula regions.
Russian officials previously confirmed that a Ukrainian drone had been downed on the outskirts of St. Petersburg on Thursday.
