The port city of Sevastopol on the Russian-annexed Crimean Peninsula was left without electricity after overnight Ukrainian drone attacks, Russian authorities said early on Wednesday.
Energy infrastructure was hit and damaged, Sevastopol's Moscow-appointed governor Mikhail Razvozhayev wrote on Telegram.
"Specialists are assessing the scale of the damage and doing everything possible to restore the power supply," he said.
According to media reports, power supplies also collapsed in some other parts of Crimea after a drone struck a power plant.
In Russian-occupied parts of the southern Ukrainian region of Kherson, authorities restored power after an outage lasting several hours.
The Volga region of Orenburg in Russia, far from the front line, also came under fire.
Governor Yevgeny Solntsev reported a major attack. "Some drones were shot down over industrial facilities in the city," he wrote on social media.
Emergency services and firefighters were deployed, but there were no injuries, he said.
According to media reports, a natural gas processing facility was targeted. The extent of any damage was not immediately known.
Russia has been waging war against Ukraine for more than four years.
As part of its defence, Kiev is also launching drone attacks on strategically important facilities deep inside Russia, including military sites and oil and gas infrastructure.
The aim of such strikes is to make it harder for the Russian military to secure fuel supplies and for the Kremlin to finance the war.
