Russia Tuesday attributed loud blasts at a key military airbase on the Moscow-annexed Crimean peninsula to exploding ammunitions, downplaying the possibility that the site was hit by Ukrainian fire.
Dramatic amateur footage shared on social media appeared to show panicked holidaymakers fleeing a Crimean beach with young children, as ballooning clouds of grey smoke rose over the horizon.
The blasts rocked the Saki airfield on the 167th day of Moscow's invasion.
Russia annexed the Crimean peninsula in 2014 and has used the region as a staging ground for its attacks on Ukraine, but it has rarely been a target for Ukrainian forces.
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The Russian defence ministry said "several aviation munitions detonated" at the base in an incident the head of the region said had left one person dead.
Local health officials earlier said five people, including one child, had been injured.
The defence ministry said it was looking to establish the reason for the explosions but indicated the airfield was not targeted in an attack.
There was no immediate reaction from Kyiv.
Ukraine's army, which for months pleaded for long-range artillery from Western allies, has been hitting targets deeper in Russian-held territory since some started arriving in recent weeks.
Kyiv has also taken credit for several acts of sabotage inside Russian-held territory.
Moscow seized Crimea from Ukraine in the wake of massive nationwide street demonstrations that led to the ouster of a Kremlin-friendly president.
Those protests precipitated fighting between the army and Moscow-backed separatists in eastern Ukraine, which would lay the groundwork for Moscow's full-scale assault on February 24 this year.
The invasion has left thousands dead, forced millions in Ukraine from their homes, and led to a deep rupture in economic ties between Russia and the West.
In response to economic sanctions against Moscow for the invasion, Russia has squeezed gas deliveries to Europe.
It announced on Tuesday that its oil deliveries through Ukraine had been halted.
Transneft, the Russian pipeline operator, said the Ukrainian side had stopped flows because it was "not receiving funds for these services".
The Ukrainian side did not comment.
One of the impacted countries, Slovakia, confirmed flows had been halted for several days, and a spokesman for Bratislava refinery Slovnaft cited "technical problems at the bank level in connection with the payment of transit fees from the Russian side".
The Kremlin lashed out after Ukrainian President Volodymyr Zelensky said in an interview that Europe should close their borders to Russians in response to the war.
The Ukrainian leader told The Washington Post that current Western sanctions against Moscow were too weak, in a call that has been echoed by Russia's neighbours Estonia and Finland.
"The irrationality of thinking in this case is off the charts," Kremlin spokesman Dmitry Peskov told reporters.
On the frontlines, Ukraine said Russia was pursuing a campaign of bombardment of the east of the country that has left much of the industrial Donbas region in ruins.
Kyiv said Tuesday it had transported at least 3,000 people out of the battle-scarred eastern region of Donetsk since it ordered evacuations ahead of winter.
The Ukrainian authorities are asking people to leave the area, as they do not expect to be able to provide it with heat during the cold winter months.
The presidency earlier said that three people had been killed and 19 more wounded in Russian shelling across the Donetsk region on Monday.
The head of the central region of Dnipro, meanwhile, said that 11 medical facilities had relocated there from the battle-torn Kharkiv and Lugansk regions further east.
"Those facilities transferred over 100 pieces of equipment and 10 ambulances," Dnipro regional governor Valentyn Reznichenko said.
"The hospitals are restarting work. They are mostly receiving displaced people."