A Ukrainian drone attack damaged an industrial facility in Russia's Saratov region, regional Governor Roman Busargin said early on February 11.
"According to preliminary information, there are no casualties," Busargin said on Telegram.
"The air-defense forces eliminated the [drones]. There is damage at an industrial enterprise in Saratov. Operational services are working in places where debris may have fallen," Busargin said.
Video posted on social media that have been verified by Radio Free Europe/Radio Liberty showed fire in the area of the facility.
The Russian Defense Ministry said air defenses intercepted and destroyed 40 Ukrainian drones overnight.
Eighteen of the drones were destroyed over the Saratov region, the ministry said on Telegram. The rest were downed over four other regions in Russia's south and west, it said.
The Russian aviation watchdog suspended flights at four airports to ensure safety.
Several unofficial Russian Telegram news channels reported explosions and fires in the area of the oil refinery in Saratov, a city on the Volga River about 725 kilometers southeast of Moscow.
A Ukrainian attack in January on an oil depot near a military air base in Engels in the Saratov region sparked a fire that took days to extinguish.
The governor of Belgorod region said earlier that Ukrainian drones attacked four villages in the region. One of the drones hit a car in Kukuyevka, injuring the driver.
Another drone attacked a residential building, piercing the roof, smashing windows, and damaging a car parked nearby, said Governor Vyacheslav Gladkov.
He said there was also a drone attack on the warehouse premises of an agricultural enterprise.
Kyiv has said its air attacks inside Russia are aimed at destroying infrastructure key to Moscow's war efforts and are in retaliation for Russia's continued attacks on Ukraine, especially its electrical infrastructure.
The Ukrainian Air Force said earlier that several groups of Russian drones attacked Ukraine late on February 10, and an air alert was declared in a number of regions.
Shaded drones were detected moving over the Odesa, Kherson, Kharkiv, Poltava, Dnipropetrovsk, and Vinnytsia regions around 11:30 p.m. local time.
The Ukrainian military advised citizens not to ignore air alerts.
The Air Force also warned that there were likely launches of Kalibr cruise missiles from the Black Sea. An air alert was declared in Kyiv and a number of regions. There were no reports of damage from the Ukrainian side.
