MOSCOW >> Russian officials accused Ukraine of targeting six Russian regions with drones early Wednesday in what appears to be the biggest drone attack on Russian soil since Moscow sent troops into Ukraine 18 months ago.

Drones hit an airport in the western Pskov region and started a massive fire there, the governor and local media reported. More drones were shot down over Oryol, Bryansk, Ryazan, Kaluga and the Moscow region surrounding the Russian capital, according to the Defense Ministry.

The strike in Pskov hit an airport in the region’s namesake capital and damaged four Il-76 transport aircraft, Russia’s state news agency Tass reported, citing emergency officials.

Pskov regional Gov. Mikhail Vedernikov ordered all flights to and from the airport canceled Wednesday so damage could be assessed during daylight.

Footage and images posted on social media showed smoke billowing over the city of Pskov and a large blaze. Vedernikov said there were no casualties, and the fire has been contained. Unconfirmed media reports said between 10 and 20 drones could have attacked the airport.

Pskov was the only region where officials reported damage. Three drones were shot down over the Bryansk region, according to the Russian military, and two over the Oryol region, its Gov. Andrei Klychkov said. Two were downed over the Ryazan region, one more over Kaluga, and one more over the Moscow region, officials said.

No damage or casualties were registered in those regions, although some Russian media cited residents of the Bryansk region as saying that they heard a loud explosion.

Also on early Wednesday, Russian-installed officials in the annexed Crimea reported repelling an attack of drones targeting the harbor of the port city of Sevastopol. Moscow-appointed governor of Sevastopol Mikhail Razvozzhayev said it wasn’t immediately clear how many of the drones have been destroyed. It wasn’t immediately clear if the attack caused any damage.