Saint Petersburg (AFP) - Ukrainian drones hit an oil complex and military base in Saint Petersburg on Wednesday as ministers and officials gathered for a flagship economic forum in Russia’s second city, officials said.

Ukrainian President Volodymyr Zelensky called the strikes “fair” retaliation for Russia’s bombardment of Ukraine and threatened more, as his country recovered from Russian drone and missile attacks on Tuesday that killed 23 people.

Some 20,000 people from 130 countries were to attend the three-day annual Saint Petersburg International Economic Forum (SPIEF) – an event once dubbed “Russia’s Davos” – which began Wednesday.

President Vladimir Putin is to give a keynote address at the forum on Friday and Kremlin spokesman Dmitry Peskov vowed Russia would give a “systemic” response to Ukraine’s strikes on the city.

The Saint Petersburg attacks damaged “several” infrastructure facilities, the city’s governor Alexander Beglov said. There were injuries but no fatalities, he added.

A drone strike on a bus in Russian-occupied east Ukraine killed at least seven people however, Russian-installed officials said.

One man was killed in the Russian region of Briansk near the Ukraine border and another civilian in the Russian-occupied Kharkiv region, officials reported.

Russia’s latest attacks left at least 10 dead across Ukraine, local officials said.

Ukraine said it hit the Saint Petersburg Oil Terminal and the city’s Kronstadt military base. Black smoke rose from behind the Peter and Paul Fortress which is among the city’s most popular tourist attractions.

- Black smoke rising -

The commander of Ukraine’s drone forces said a Russian warship was hit at the Kronstadt naval base, posting black-and-white drone footage of what he said was the attack.

Saint Petersburg’s main airport closed for hours, while several flights from Moscow to the northern capital were delayed.

Ukrainian officials said the attack aimed to disrupt the conference.

“The Petersburg forum is opening with a nice plume of black smoke in the background after Ukrainian strikes,” said Sergiy Sternenko, an adviser to the Ukrainian defence minister.

Smoke was visible from the conference venue as the first sessions started. Valeria, a 32-year-old businesswoman from Moscow at the forum told AFP she was used to the threat of attacks.

“We have been living under such attacks for many years now,” she said.

During a press conference in Kyiv with NATO chief Mark Rutte, Zelensky said Ukraine was responding “accordingly” to Russian bombardment.

“It’s just a matter of time before we can scale up the intensity of our responses,” he said.

Rutte said Ukraine was showing success taking out “some of the key capabilities and capacities of the Russians”.

EU foreign affairs chief Kaja Kallas told AFP that Ukraine’s attacks had spooked the Kremlin.

“It clearly shows also panic on the Russian side – why they are increasing the terrorist attacks that they’re doing in Ukraine is because they don’t know what to do with these things,” Kallas said in an interview.

“Putin is losing money, men, and momentum, and that’s why he’s increasing attacks on civilians.”

- Russia’s Davos -

Since Russia launched its full-scale assault on Ukraine in February 2022, SPIEF – previously Moscow’s premier economic event for courting Western investment – has been seen as a snapshot of Russia’s isolation on the world stage.

French President Emmanuel Macron, then-German Chancellor Angela Merkel, and the late Japanese Prime Minister Shinzo Abe were among those who addressed the forum alongside Putin in the past.

Now Russia can only rely on its closest allies to attend. This year, the presidents of Uzbekistan and Tanzania will be present, alongside ministers from Cuba, Belarus, the United Arab Emirates and Saudi Arabia.

The Kremlin’s economy envoy Kirill Dmitriev said the forum was a gathering of “sovereign countries”, slamming “globalist” rivals like the annual Davos gathering in Switzerland.

UN Secretary General Antonio Guterres – who on Tuesday condemned Russian strikes on Ukraine – will speak at a panel on the environment on Friday.

The United States is sending Rodney Mims Cook Jr, head of the US Commission of Fine Arts who is overseeing President Donald Trump’s new White House ballroom, to the event. He will speak on a panel titled “Russia–US: A Cultural Dialogue”.

Several fringe figures from Western countries have also been invited – including right-wing commentator Candace Owens, Putin-backing US actor Steven Seagal and representatives of the far-right Alternative for Germany party.

Andrew Tate, the British-American self-described misogynist charged in Romania with human trafficking and accused of rape, landed in Moscow on Tuesday, triggering speculation he would attend the forum.