Russian forces have intercepted 86 drones in the area around St. Petersburg, where a major investment forum is taking place, the region's governor Alexander Drozdenko said on Telegram, quoted by Agence France-Presse.
"Eighty-six drones were shot down over the Leningrad Region. Combat operations continue", the message on Telegram reads.
"St. Petersburg was the target of a large-scale attack with military drones", said the city's governor Alexander Beglov. "I urge the residents of St. Petersburg to stay home and not go out," he added.
Pulkovo International Airport, south of the city, announced a temporary suspension of flights, without specifying the reason.
On Wednesday, at the opening of the St. Petersburg Forum - once called the "Russian Davos" by analogy with the World Economic Forum - Ukrainian drones struck an oil installation and a nearby military facility. Guests arriving at the event were greeted by a cloud of black smoke in the background.
The forum ends today, a day after a statement by Russian President Vladimir Putin.
In total, the Russian Defense Ministry reported the interception of 376 Ukrainian drones overnight over the country. Moscow Mayor Sergei Sobyanin said eight drones were shot down as they headed toward the city.
Ukraine has recently stepped up drone strikes on occupied territories and Russia in response to daily Russian bombing of its territory.
A drone attack caused a fire of about 5,000 square meters at a fuel depot in Ust-Labinsk, in Russia's Krasnodar region, according to local authorities.
In Ukraine's Zaporizhia region, a Russian drone attack on "vital and industrial infrastructure" caused the deaths of two people, local military commander Ivan Fyodorov reported.
In the Dnipropetrovsk region, which was "fired nearly 30 times with drones and artillery", one person was killed and three were injured in the Kryvyi Rih region, the head of the regional military administration, Oleksandr Ganza, reported.
Ukrainian rescue services also reported drone attacks on the city of Odessa.