Russia and Ukraine struck each other with hundreds of drones on Sunday, throwing Russian air travel in disarray, days after Moscow launched its largest aerial assault in the more than 3-year-old war.

Photos circulating on social media showed crowds huddling at Russian airports including key international hubs in Moscow and St. Petersburg, as hundreds of flights were delayed or canceled due to Ukrainian drone strikes on Saturday and overnight, according to Russia’s Transport Ministry.

The flight disruptions hit Moscow’s Sheremetyevo and St. Petersburg’s main Pulkovo airports. Other airports in western and central Russia also faced disruptions.

Russian air defenses shot down 120 Ukrainian drones during the nighttime attacks, and 39 more before 2 p.m. Moscow time (11 GMT) on Sunday, Russia’s Defense Ministry said. It did not clarify how many had hit targets, or how many had been launched in total.

Early on Sunday, Ukrainian drones injured two civilians in Russia’s Belgorod region near the border, its Gov. Vyacheslav Gladkov said Sunday.

The Ukrainian attacks came just days after Russia pummelled Kyiv with waves of drones and missiles overnight into Friday, in what Ukrainian officials called the largest such strike since Moscow’s all-out invasion. The seven-hour onslaught killed at least two civilians, wounded dozens more and caused widespread damage, Ukraine said, while Moscow ramped up its push to capture more of its neighbor’s land.

In total, Russia launched 550 drones and missiles across Ukraine that night, according to the country’s air force. The barrages have coincided with a concerted Russian effort to break through parts of the roughly 1,000-kilometer (620-mile) front line, where Ukrainian troops are under severe pressure.

Large-scale Russian drone strikes on Sunday injured three civilians in Kyiv and at least two in Kharkiv, Ukraine’s second-largest city in the northeast, officials said. A large Russian attack involving Shahed drones also targeted port infrastructure in Mykolaiv in central Ukraine, according to local Gov. Vitaliy Kim. He reported warehouses and the port’s power grid were damaged but there were no casualties.

Hours later, Russia launched a glide bomb and a drone at the front-line town of Kostyantynivka in eastern Ukraine, killing four civilians and injuring a fifth, the prosecutor’s office said. The drone struck a car in which a married couple were travelling, killing the 39-year-old woman and 40-year-old man on the spot, it said.

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