A Ukrainian drone dropped explosives on a substation in a Russian village close to the border on Friday, cutting off the power supply to a hospital, the regional governor said.
In Belaya, less than 25 kilometres (16 miles) from the border, "a Ukrainian drone dropped two explosive devices on a substation", Kursk regional governor Roman Starovoyt said on the messaging platform Telegram.
"One of the transformers caught fire. Five settlements and a hospital were cut off from power supply. Fire crews rushed to the scene," he added.
"Power will be restored as soon as it is safe to do so."
Russia earlier said it had destroyed two Ukrainian drones over the neighbouring Belgorod region.
The defence ministry said the first drone was "thwarted" at about 5:00pm (1400 GMT) on Thursday.
A second drone was brought down around four hours later.
"The Ukrainian unmanned aerial vehicle was destroyed over Belgorod region by air defence systems on duty," the ministry said on Telegram.
Belgorod and Kursk, south of Moscow, border eastern Ukraine.
Since Ukraine launched its counter-offensive in early June, Russia has weathered waves of drone attacks that have sporadically damaged buildings, including in Moscow.
Russian officials have downplayed their significance.