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

Ukraine Strikes Back

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.

The Russian Defense Ministry said air defenses 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.

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.

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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 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.

Continued Conflict

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 5 kilometers (3 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 defenses at other points along the roughly 1,000-kilometer (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.