A massive drone attack on Tuesday saw hundreds of Ukrainian aircraft attack Russia, including the biggest-ever drone swarm to have struck the capital.

At least two workers have been confirmed killed, and 18 others injured in the massive assault. A total of 337 drones were downed in the country, including 91 in Moscow alone. According to Russian officials, the attack prompted the city’s four airports to shut down temporarily.

The attack came as U.S. officials were set to discuss an end to the war with a Ukrainian delegation in Saudi Arabia. It also occurred as Russian forces have been attempting to cut off thousands of Ukrainian soldiers in the country’s western region of Kursk. A large share of the drone attacks on Tuesday (126) occurred over this region.

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Following the incident, Moscow Mayor Sergei Sobyanin confirmed it was the largest drone attack ever to hit his city.

At over 21 million people, Moscow and its surrounding region is one of the largest metropolitan areas in Europe.

One senior Russian lawmaker floated the idea of responding to the attack by hitting Ukraine with the Oreshnik hypersonic missile. This is the same weapon that Russia used against Ukraine last November after the U.S. and U.K. gave Kyiv the green light to strike deeper into Russian territory using advanced weapons supplied by the West.

Despite the violent incident, Muscovites appeared to carry on with business as usual. While flights were briefly suspended, they were later allowed to resume.

The fighting in Eastern Europe has been characterized by brutal drone warfare used by both sides. The two foes have worked to improve their drone arsenal while also devising ways to protect against them, with Russia building miles of mesh net tunnels over vulnerable routes to help protect soldiers from the modern, but often crude, weapon.

Last month, The Dallas Express reported that a drone strike hit the protective shelter surrounding Reactor 4 at the Chernobyl Nuclear Power Plant. Ukraine claims Russia was behind the attack, but Moscow denies the allegations.