Ukrainian drones struck energy and military facilities in Saint Petersburg on Wednesday, damaging infrastructure on the outskirts of Russia’s second-largest city as the country opened its flagship economic forum.

Russian officials said several infrastructure sites were hit, though no fatalities were reported. Saint Petersburg Governor Alexander Beglov said “several” facilities sustained damage and that emergency and clean-up operations were underway.

The attack coincided with the opening of the Saint Petersburg International Economic Forum, a high-profile annual gathering often referred to as “Russia’s Davos.” Russian President Vladimir Putin is expected to attend the event and deliver a keynote address on Friday.

Ukrainian officials said the strikes were intended to disrupt the forum and demonstrate Kyiv’s ability to target strategic locations deep inside Russian territory.

Witnesses cited by Reuters reported seeing thick black smoke rising over the edge of the city following the attacks.

Ukrainian President Volodymyr Zelenskyy said the drones had struck the Saint Petersburg Oil Terminal and the Kronstadt military base. He described the operation as part of Ukraine’s strategy of targeting Russian energy and military infrastructure through what Kyiv calls “long-range sanctions.”

“Ukraine’s plan for long-range sanctions is being implemented exactly as needed to bring peace closer,” Zelenskyy said in a social media post, which included footage showing a burning oil facility.

Russian authorities had issued text-message alerts to residents and visitors ahead of the strikes, warning of possible drone attacks.

The incident overshadowed the opening day of the economic forum, one of Russia’s most important business and investment events. Smoke from the affected areas was reportedly visible from the forum venue.

“The Petersburg forum is opening with a nice plume of black smoke in the background after Ukrainian strikes,” Sergiy Sternenko, an adviser to Ukraine’s Defense Ministry, said in a statement.