Ukrainian drones hit energy and military sites in St Petersburg on Wednesday as officials gathered for a flagship economic forum in the city, Russian and Ukrainian authorities said.

Some 20,000 guests from 130 countries are set to attend the three-day annual Saint Petersburg International Economic Forum – an event that was once Russia's premier gathering to court Western investors and businesses – which starts on Wednesday.

The strikes come a day after a barrage of Russian missiles and drones killed 23 people across Ukraine.

St Petersburg Governor Alexander Beglov said several infrastructure facilities were damaged, but no one was killed in the attack.

Drones hit the St Petersburg Oil Terminal and the Kronstadt military base in the city, Ukrainian President Volodymyr Zelensky said, the latest in a series of retaliatory attacks that Kyiv calls "long-range sanctions".

"Ukraine's plan for long-range sanctions is being implemented exactly as needed to bring peace closer," he said on social media, posting a video of an oil depot ablaze.

The attacks forced St Petersburg's main airport to close for hours overnight.

Ukrainian officials said the attack was aimed at disrupting the three-day gathering, which Russian President Vladimir Putin will attend and make a keynote address on Friday.

"The Petersburg forum is opening with a nice plume of black smoke in the background after Ukrainian strikes," Sergiy Sternenko, an adviser to the Ukrainian defence minister wrote on social media, posting a video of delegates walking to the venue with smoke visible in the background. (AFP)


Edited by Tony Sabine