A series of explosions rocked southwestern Russia and the Russian-occupied peninsula of Crimea early Friday as fuel depots, oil refineries and power facilities came under attack in what Moscow said was a huge Ukrainian assault involving more than 100 drones.
Although the full extent of the damage caused was unclear, the Russian authorities reported that an electricity substation was hit in the Crimean city of Sevastopol, leading to rolling blackouts.
Fires also broke out at several oil facilities in southwestern Russia, including in the port of Novorossiysk, which operates an important oil terminal.
The barrage came as Ukrainian forces are struggling to contain a new Russian offensive in their country’s northeast, while facing continued attacks along the 600-mile front line.
For the past several months, Ukraine has sought to disrupt Moscow’s military operations and put pressure on the Russian economy by inflicting damage away from the front, targeting logistical hubs and energy facilities.
The Ukrainian authorities did not immediately comment on the attack.
The attack on Novorossiysk was particularly noteworthy because it was the first time that Ukraine had targeted oil facilities there, according to Damien Ernst, an energy expert and professor at the University of Liège, Belgium.
Novorossiysk is a major port for oil exports, with about 1.5 million barrels of Russian oil passing through each day, Mr. Ernst said. If the attack caused serious damage to oil facilities there, it could have consequences for the Russian oil industry, which has been repeatedly targeted by Ukrainian drone attacks in recent months.
Schools have been closed across Sevastopol, a city of about a half-million people on the Black Sea, Mikhail Razvozhaev, the Russian-backed governor of the city, said on Telegram after the attack. He added that repairs to the substation that had been hit would take about a day and that the resulting power shortages would force the authorities to introduce rolling blackouts.
Internet connectivity in Sevastopol dropped to about 16 percent, according to NetBlocks, a web monitoring group.
It was the third attack in two days against Sevastopol. A day before, the local authorities reported Ukrainian missile attacks on the Belbek military airfield outside the city. Satellite images of the aftermath of the attack verified by The New York Times showed that three Russian jets had been completely destroyed and another had been damaged.
Crimea and Russian Black Sea ports have long been a prime target for the Ukrainian military. Ukrainian attacks there have three main objectives: reducing Russia’s capacity to use Crimea as a launchpad for missile and drone attacks; disrupting supply lines that funnel fuel and ammunition to the battlefield; and degrading the Russian fleet docked in the region to ease the pressure on Ukrainian operations in the Black Sea, such as exporting grain.
After Russia withdrew last summer from an agreement allowing Ukraine to resume some export shipments through the sea, Ukraine’s military began a campaign to drive out the Russian Navy there.
It destroyed many of Russia’s warships and attacked its headquarters in Sevastopol, forcing many ships to be moved to Novorossiysk, farther from Ukrainian territory.
The operation allowed Ukraine to establish a new shipping corridor, and seaborne grain and oilseed exports are nearing prewar levels, according to data shared with The New York Times.