June 3 (UPI) — Ukrainian drones struck targets in and around the Russian city of St. Petersburg early Wednesday ahead of a major international business and investment conference hosted by Russian President Vladimir Putin and due to be attended by representatives from 130 countries.

Footage showed loud blasts and delegates arriving for the showcase St. Petersburg International Economic Forum amid a backdrop of black smoke billowing from the nearby St. Petersburg Oil Terminal, one of the country’s largest one fuel storage and export facilities.

Flights were disrupted at St. Petersburg’s Pulkovo Airport with dozens delayed or diverted to other airports while the governor of the surrounding Leningrad province, Aleksandr Drozdenko, said that air defenses had downed 59 drones over the region.

Parts of neighboring Latvia and Estonia issued air raid warnings.

Ukrainian President Volodymyr Zelensky hailed what he called the “long-range sanctions” which he said were a joint effort by the Ukrainian security service, military intelligence, special forces, UAV systems forces and the border guard service.

“Important targets in Russia were hit last night, including the St. Petersburg oil terminal. From our state border of Ukraine to this jewel of the Russian oil industry, which works for war, there are about 1,100 kilometers. Purely military targets at the Kronstadt base were also hit. Thank you to our soldiers for their accuracy. The Ukrainian long-range sanctions plan is being implemented exactly as it is needed to bring peace closer,” he wrote on Telegram.

No deaths were reported, but the Kremlin vowed to retaliate.

“Our responses will be systemic in nature,” said spokesman Dmitry Peskov.

The United States is due to be represented by a small delegation led by Rodney Mims Cook Jr., chair of the U.S. Commission of Fine Arts after U.S. President Donald Trump declined to send a representative in 2025.

Cook, who is supervising Trump’s project to construct a new White House ballroom on the site formerly occupied by the East Wing, is an expert on Russian architecture and has led restorations of historic buildings there, will be participate in sessions promoting U.S.-Russia cultural ties.

The American Chamber of Commerce in Russia will also be in attendance.

Former U.K. Defense Attache to Moscow John Foreman told the Kyiv Independent that it was humiliating for Putin for his home city to come under attack on the opening day of the forum.

“Instead of being able to project a narrative of inevitable victory and strength, the opposite is true and won’t be lost on attendees,” Foreman said.