A drone has exploded outside the Russian city of Kaluga, regional governor Vladislav Shapsha said on Monday, adding that no-one was injured in the blast.
"It has been established that the drone exploded in the air at an altitude of 50 meters in the forest near the city at five o'clock in the morning," he wrote on Telegram.
Kaluga is about 150 km (93 miles) south west of Moscow and 260 km (162 miles) from the Ukrainian border.
The governor did not make clear the source of the drone.
Russia has said in the past that Ukrainian drones have flown into its territory and caused damage to civilian infrastructure, an assertion that Kyiv denies.