A massive Ukrainian drone attack on Crimea early on Friday caused power cutoffs in the city of Sevastopol and set a refinery ablaze in southern Russia, Russian authorities said.

The drone raids marked Kyiv’s attempt to strike back during Moscow’s offensive in northeastern Ukraine, which has added to the pressure on outnumbered and outgunned Ukrainian forces who are waiting for delayed deliveries of crucial weapons and ammunition from Western partners.

A Ukrainian intelligence official confirmed to The Associated Press that Ukraine’s Security Service and Military Intelligence conducted a joint operation to strike Russia’s military infrastructure sites in Novorossiysk, on the Black Sea coast, and occupied Sevastopol.

The official spoke on condition of anonymity, because they were not authorised to comment publicly.

The Russian Defence Ministry said air defences downed 51 Ukrainian drones over Crimea, another 44 over the Krasnodar region and six over the Belgorod region.

It said Russian warplanes and patrol boats also destroyed six sea drones in the Black Sea.

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A destroyed MiG 31 fighter aircraft and fuel storage facility at Belbek air base, near Sevastopol (Satellite image ©2024 Maxar Technologies via AP)

Mikhail Razvozhayev, the governor of Sevastopol, which is the main base for Russia’s Black Sea Fleet, said the drone attack damaged the city’s power plant. He said it could take a day to fully restore energy supplies and warned residents that power would be cut to parts of the city.

“Communal services are doing their best to restore the power system as quickly as possible,” he said in a statement.

Mr Razvozhayev also announced that schools in the city would be closed temporarily.

Earlier, Ukrainian attacks damaged aircraft and a fuel storage facility at Belbek air base near Sevastopol, according to satellite images released by Maxar Technologies.

In the Krasnodar region, the authorities said a drone attack early on Friday caused a fire at an oil refinery in Tuapse which was later contained. There were no casualties.

Ukraine has repeatedly targeted refineries and other energy facilities deep inside Russia, causing significant damage.

Ukrainian drones also attacked Novorossiysk, a major Black Sea port. The Krasnodar region’s governor, Veniamin Kondratyev, said fragments of downed drones caused several fires but there were no casualties.

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A damaged house after a Russian airstrike in Vovchansk, Ukraine (Evgeniy Maloletka/AP)

Belgorov governor Vyacheslav Gladkov said a Ukrainian drone struck a vehicle, killing a woman and her four-year-old child. Another attack set a fuel tank ablaze at a gas station in the region, he said.

Meanwhile, Ukrainian troops were fighting to halt Russian advances in the northeastern Kharkiv region that began late last week.

The town of Vovchansk, located just five kilometres (three miles) from the Russian border, has been a hot spot in the fighting in recent days.

Ukrainian authorities have evacuated some 8,000 civilians from the town. The Russian army’s usual tactic is to reduce towns and villages to ruins with aerial strikes before its units move in.

Russia has also been testing defences at other points along the roughly 1,000-km (620-mile) front line snaking from north to south through eastern Ukraine.

That line has barely changed over the past 18 months in what became a war of attrition.

Recent Russian attacks have come in the eastern Donetsk region, as well as the Chernihiv and Sumy regions in the north and in the southern Zaporizhzhia region.

The apparent aim is to stretch depleted Ukrainian resources and exploit weaknesses.

By starting the new offensive, Russian troops “expanded the zone of active hostilities by almost 70 kilometres” (about 45 miles), in an effort to force Ukraine to spread its forces and use reserve troops, Ukraine’s military chief Colonel General Oleksandr Syrskyi said on Friday.

In the Kharkiv region, Russian forces have advanced 10 kilometres from the border, President Volodymyr Zelensky told reporters on Friday.