Dec. 21 (UPI) -- Activity at three airports was restricted Saturday after eight Ukrainian drones struck deep inside Russia in the city of Kazan, the Russian authorities said. The assault came between 7:40 a.m. and 9:20 a.m. local time, and targeted "civilian infrastructure facilities" in Kazan with eight aircraft-type UAVs coming in three waves from different directions, the Russian Defense Ministry said on its Telegram channel . Advertisement Russian air defense systems shot down three drones,