Ukraine said the "strongest" shelling by Moscow so far of the southern city Mykolaiv killed a grain tycoon Sunday, as Russia claimed an attack from a drone wounded six personnel at the headquarters of its Black Sea fleet in annexed Crimea.
AFP journalists witnessed intense Russian bombardment of the eastern town of Bakhmut after President Volodymyr Zelensky called for civilians to leave the front line Donetsk region bearing the brunt of the Kremlin's offensive.
Russian authorities in the Crimean Black Sea peninsula — seized by Moscow from Ukraine in 2014 — said a small explosive device from a commercial drone, likely launched nearby, hit the navy command in Sevastopol.
The local mayor blamed "Ukrainian nationalists" for the attack that forced the cancellation of festivities in the city marking Russia's annual holiday celebrating the navy.
But Ukraine's navy accused Russia of staging the attacks as a pretext to cancel the festivities.
"Russia fears holding a parade in the Black Sea, but announces a plan to dominate the high seas," said presidential adviser Mykhailo Podolyak.
The claim and counterclaim come as the dispute over which side struck a jail holding Ukrainian prisoners of war in Kremlin-controlled Olenivka, rumbled on, with Kyiv and Moscow trading blame.
Russia's defense ministry said Sunday it had invited the International Committee of the Red Cross (ICRC) and the United Nations to visit the site "in the interests of an objective investigation."
But the ICRC said Sunday it had yet to receive approval to enter the site in a region where it has been active since 2014 following the eruption of violence between Ukrainian forces and pro-Russian separatists.
"We are ready to deploy," the ICRC said. "It is imperative that the ICRC be granted immediate access."
Dozens killed in jail strike
Russia's military said that 50 Ukrainian servicemen died, including troops who had surrendered after weeks of fighting off Russia's brutal bombardment of the sprawling Azovstal steelworks in the port city of Mariupol.
Ukraine says Russia was behind the attack, with Zelensky accusing Moscow of the "deliberate mass murder of Ukrainian prisoners of war."
He has stepped up calls for the international community, especially the United States, to have Russia officially declared a "state sponsor of terrorism."
Authorities in Ukraine's southern city of Mykolaiv said Sunday that widespread Russian bombardments overnight had left at least two civilians dead, as Moscow continued to pummel the sprawling front line.
"Mykolaiv was subjected to mass shelling today. Probably the strongest so far," the city's mayor Oleksandr Senkevych wrote on Telegram.
The authorities said leading Ukrainian agricultural magnate Oleksiy Vadatursky, 74, and his wife Raisa were killed when a missile struck their house.
Vadatursky, who was ranked Ukraine's 24th richest man with a fortune worth $430 million by Forbes, owned major grain exporter Nibulon and was previously decorated with the prestigious "Hero of Ukraine" award.
Podolyak, the presidential adviser, said his death was "not an accident but a well-planned and organized deliberate murder."
Mykolaiv — which has been attacked frequently — is the closest Ukrainian city to the southern front where Kyiv's forces are looking to launch a major counter-offensive to recapture territory lost after Russia's February invasion.
Strikes also pounded the northeastern regions of Kharkiv and Sumy, near the front line with the Russian forces.
Sumy regional chief Dmytro Zhyvytsky said that some 50 strikes on Saturday evening had left one person dead and two wounded.
The governor of the Donetsk region, where Moscow is focusing the brunt of its attacks, said three civilians were killed and eight wounded in shelling Saturday.
AFP journalists on Sunday saw one wounded man collected by an ambulance after a ferocious bombardment of the town of Bakhmut.
In an overnight address Zelensky warned that thousands of people, including children, were still in the battleground areas of the Donetsk region.
"There's already a governmental decision about obligatory evacuation from Donetsk," Zelensky said, underscoring authorities' calls to leave the besieged region in recent weeks.
"Leave, we will help," Zelensky said. "At this stage of the war, terror is the main weapon of Russia."
Official Ukrainian estimates put the number of civilians still living in the unoccupied area of Donetsk at between 200,000 and 220,000.
A mandatory evacuation notice posted Saturday evening said the coming winter made it a matter of urgency, particularly for the more than 50,000 children still in the region.
Kateryna Novakivska, a deputy commander of a Ukrainian unit, said she was fighting so her comrades could be reunited with their families.
"The morale of our servicemen is at a high level now, but everyone wants to visit their homes, see their relatives and loved ones," she said.
The intense bombardments around Ukraine come as the authorities push to restart grain exports under a plan brokered by the UN and Turkey to lift a Russian naval blockade.
A spokesman for the Turkish presidency said there was a "high probability" that a first ship carrying Ukrainian grain could leave Ukraine on Monday.