A huge fire erupted in Moscow-annexed Crimea after a suspected drone attack hit an oil depot on Saturday, as fighting intensified on the southern Ukrainian front and shelling deprived Russian border villages of power.
The attacks came one day after Kyiv said preparations for a long-awaited counteroffensive were nearly complete, having vowed to expel Russian forces from territory they seized in the east and south following their 2022 invasion.
On Friday, a Russian strike on a bloc of flats in the central Ukrainian city of Uman killed 23 people, including a baby boy.
On Saturday, officials in Moscow-controlled Crimea, towns under Russian occupation in southern Ukraine and a governor of a border region reported attacks.
Fears of Ukrainian reprisals more than a year into Moscow's offensive have grown in Russia, where a range of cities have cancelled traditional May 9 celebrations to mark Soviet victory over the Nazis at the end of World War II in 1945.
In Sevastopol, home to Russia's Black Sea Fleet, clouds of smoke rose high into the sky as a fuel reserved burned.
The port city has been hit by a series of drone attacks since Moscow's invasion of Ukraine began more than a year ago.
- 'God's punishment' -
Russian-installed authorities said the fire was caused by a suspected drone but sought to downplay the incident, amid rising security fears on the peninsula.
The Kremlin said nothing about the attack.
It came less than 24 hours after Russia struck a typical Soviet-era housing bloc in the historic city of Uman, killing more than two dozen of its residents.
Kyiv on Saturday identified five children killed in the attack as an 18-month-old boy, three girls aged eight, 11 and 14, and a 16-year-old boy.
"One woman is considered missing. The search continues," Ukrainian Interior Minister Ihor Klymenko said.
Ukraine did not claim the Crimea attack, but military intelligence implied it was revenge for Uman.
Andriy Yusov, from the defence ministry's intelligence unit, said it was "God's punishment, in particularly for the civilians killed in Uman."
He warned people in Crimea to "avoid being near military facilities and facilities providing the aggressor's army in the near future."
- 'Intense shelling' -
On the Russian-annexed peninsula, the governor of Sevastopol, Mikhail Razvozhayev, urged Crimeans to "remain calm" and said "nobody was hurt."
He estimated the fire was "around 1,000 square metres" (10,764 square feet).
Razvozhayev insisted that the peninsula's reserves were not impacted and that authorities had enough fuel for all civilian needs.
Earlier this week, Moscow said it had repelled a drone strike on Crimea -- annexed by Russia in 2014 and used as a launchpad for its invasion.
In southern Ukraine, Russian occupation authorities said a key city they control -- Novaya Kakhovka -- had come under "intense shelling" and had been cut off from power.
The city fell to Russian forces on the first day of their invasion on February 24, 2022. It lies in the part of the Kherson region that Moscow still controls, having withdrawn from the eponymous regional capital last November.
Russian forces urged people in the city "to keep calm" and said that work to restore power will start "after the shelling ends."
- Russian border villages shelled -
The shelling of Novaya Kakhovka came a day after Russian shelling killed a 57-year-old woman in a southern Ukrainian village, with Ukraine's President Volodymyr Zelensky vowing a response.
Inside Russia, security fears have grown amid talk of a Ukrainian counteroffensive.
The governor of the border Belgorod region -- that has also been hit by a series of attacks throughout the war -- said Saturday that five frontier villages were without power after Ukrainian shelling.
"The power lines are damaged," Gladkov said, adding that there were no victims.
He said an uninhabited house had been hit and promised to restore power quickly.
Elsewhere, Russia accused Poland -- with whom it has historically poor relations -- of a "blatant violation" of international norms after Warsaw impounded a school run by the Russian embassy in the Polish capital.
Moscow called the move an "illegal act" and promised "harsh" consequences against Warsaw.