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

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, according to Reuters.