The blogger, Vladlen Tatarsky, 40, was an ardent supporter of the war in Ukraine and filed regular reports on the fighting from the front lines. He was killed Sunday as he led a discussion at a riverside cafe in the historic heart of St. Petersburg, Russia’s second-largest city.

Russian authorities described the bombing as an act of terrorism and blamed Ukrainian intelligence agencies for orchestrating it.

Police arrested 26-year-old St. Petersburg resident Darya Trepova, who was seen on video moments before the blast presenting Tatarsky with a statuette that is believed to have contained explosives.

The Interior Ministry released a video in which Trepova told a police officer that she brought the bust to the cafe. When asked who gave it to her, she said she would explain later. The circumstances under which Trepova spoke were unclear, including whether she was under duress.

The National Anti-Terrorist Committee, which coordinates counterterrorism operations, said the bombing was “planned by Ukrainian special services.” It said Trepova was an “active supporter” of imprisoned Russian opposition leader Alexei Navalny. Last year, she was arrested and spent 10 days in custody after taking part in an anti-war rally.

Ukrainian authorities did not directly respond to the accusation, but President Volodymyr Zelensky said in reference to the attack that he doesn’t think about events in Russia, and his top adviser described the bombing as part of Russia’s internal turmoil.

While Trepova was arrested in St. Petersburg, her case was sent to Moscow, where the country’s top investigative agencies are headquartered, an apparent reflection of its high priority.

In a closed-door hearing, Moscow’s Basmanny District Court ordered Trepova to remain in custody until June 2 pending the investigation. Russian law suggests a life sentence for terrorism-related crimes, but life terms aren’t handed down to women, who instead face sentences of up to 20 years in prison.

According to Russian media reports, Trepova told investigators she was asked to deliver the bust but didn’t know what was inside it.

The bombing injured 40 other people, 25 of whom have been hospitalized. It 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. Tatarsky, who joined separatists in eastern Ukraine after a Moscow-backed insurgency erupted there in 2014, fought on the front lines for years before turning to blogging.

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