The Russian city of St. Petersburg was targeted by a fresh barrage of long-range Ukrainian drones on Saturday as an international economic forum in the city came to a close.

In the Leningrad Region which surrounds St. Petersburg (formerly known as Leningrad), local governor Alexander Drosdenko said air defenses shot down 141 drones in an "unprecedented attack," while people within the city were warned to take shelter.

"In accordance with the recommendations of the emergency response team, I ask the residents of St. Petersburg to stay in their homes and not to go out onto the streets," city governor Alexander Beglov wrote on Telegram, adding: "There may be interruptions to mobile internet."

The nearby island of Kronstadt in the Gulf of Finland, home to Russia's Baltic Fleet, was also targeted, causing a fire. "Such special operations weaken the Baltic Fleet," said the Ukrainian Security Service (SBU), claiming to have hit missile and ammunition arsenals.

Just to the south of Kronstadt on the Russian mainland, local media reported that 600 people had to leave their homes in the coastal town of Bolshaya Ishora, while St. Peterburg's Pulkovo Airport, used by many of the economic forum's international guests, temporarily halted flights.