At least three people were injured in Ukrainian drone attacks on Russia's border region of Belgorod, the governor, Vyacheslav Gladkov, said on Telegram on Thursday.
All were taken to hospital. He said the building of the regional administration was among the targets hit.
In the southern Volgograd region, a drone strike caused a fire and a leak at an oil refinery after debris from a downed drone fell on the site, according to Governor Andrei Bocharov.
The Russian Defence Ministry said a total of 44 Ukrainian drones were intercepted overnight.
Ukraine, in its fight to repel Russia's three-and-a-half-year invasion, frequently targets sites deep inside Russian territory.
