Russia’s top security agency on Thursday accused a Ukrainian man of involvement in a bombing that killed a well-known Russian military blogger at a St. Petersburg cafe.

Vladlen Tatarsky, 40, an ardent supporter of the war in Ukraine who filed regular reports on the fighting from the front lines, was killed on April 2 as he led a discussion at a riverside cafe in the historic heart of St. Petersburg, Russia’s second-largest city. Over 50 people were injured.

A 26-year-old St. Petersburg resident, Darya Trepova, who was seen on video moments before the blast presenting Tatarsky with a statuette that contained explosives, was quickly arrested. According to Russian media reports, Trepova told investigators she was asked to deliver the statuette but didn’t know what was inside it.

Russian authorities described the bombing as an act of terrorism and blamed Ukrainian intelligence agencies for orchestrating it. Ukrainian authorities have not directly responded to the accusation, but an adviser to Ukrainian President Volodymyr Zelenskyy described the bombing as part of Russia’s internal turmoil.

On Thursday, the Federal Security Service, known under its Russian acronym FSB, declared that a Ukrainian citizen whom it identified as Yuriy Denysov, had gathered information about the blogger and provided Trepova with explosives delivered via courier service. The agency claimed that Denysov was acting on orders from the Ukrainian security services and left Russia the day after the bombing.

The FSB also reaffirmed that Trepova was a supporter of imprisoned Russian opposition leader Alexei Navalny and accused Navalny’s top allies of making repeated calls for subversive activities in Russia.

Navalny associates have rejected previous similar accusations and warned that the authorities could try to use the explosion to extend Navalny’s prison term and cast his supporters as an “internal enemy.”

The bombing was the latest attack inside Russia on a high-profile pro-war figure. Last year, a nationalist TV commentator was assassinated when a bomb exploded in her SUV outside Moscow.

Tatarsky was the pen name of Maxim Fomin, who had accumulated more than 560,000 followers on his Telegram messaging app channel. He had joined separatists in eastern Ukraine after a Moscow-backed insurgency erupted there in 2014 and fought on the front lines for years before turning to blogging.

Military bloggers have become increasingly visible in Russia, supporting the war but also exposing flaws in military strategy while the Kremlin has shut down independent media outlets and muzzled any criticism of the war.