Ukrainian drones targeted St Petersburg on Sunday, Russian authorities said, forcing the airport to close for five hours as Russian President Vladimir Putin marked the country’s Navy Day in the city, despite the earlier cancellation of its naval parade due to security concerns.

St Petersburg usually holds a large-scale, televised navy parade on Navy Day, which features a flotilla of warships and military vessels sailing down the Neva River and is attended by Putin.

Last year, Russia suspected a Ukrainian plan to attack the city’s parade, according to state television.

Kremlin spokesman Dmitry Peskov confirmed on Sunday that this year’s parade had been cancelled for security reasons, following first reports of its cancellation in early July.

Putin arrived at the city’s historic naval headquarters on Sunday by a patrol speed boat, from where he followed drills involving more than 150 vessels and 15,000 military personnel in the Pacific and Arctic Oceans and Baltic and Caspian Seas.

“Today we are marking this holiday in a working setting, we are inspecting the combat readiness of the fleet,” Putin said in a video address.

The Russian Defence Ministry said air defence units downed a total of 291 Ukrainian fixed-wing drones on Sunday, below a record 524 drones downed in attacks on May 7, ahead of Russia’s Victory Day parade on May 9.

Alexander Drozdenko, governor of the Leningrad region surrounding St Petersburg, said that over 10 drones were downed over the area, and falling debris injured a woman. At 8:40 GMT (1:40 pm PST) on Sunday, Drozdenko said that the attack was repelled.

St Petersburg’s Pulkovo airport was closed during the attack, with 57 flights delayed and 22 diverted to other airports, according to a statement. Pulkovo resumed operations later on Sunday.

Russian blogger Alexander Yunashev, part of an official group of reporters travelling with Peskov, said Peskov had told him their flight from Moscow to St Petersburg had been delayed by the drone attack for two hours on Sunday.