Russia’s top counterterrorism body on Monday blamed Ukrainian intelligence agencies for the bombing attack that killed a well-known Russian military blogger who fervently supported Moscow’s war in Ukraine.

Russian officials said Vladlen Tatarsky, 40, was killed Sunday as he was leading a discussion at a cafe on the banks of the Neva River in the historic heart of St. Petersburg. More than 30 were wounded by the blast, and 10 are in grave condition, according to the authorities.

The National Anti-Terrorist Committee, a state structure that coordinates counterterrorism operations, said the “terrorist act” against Tatarsky was “planned by Ukrainian special services” with the involvement of people who have cooperated with an anti-corruption foundation created by the jailed Russian opposition leader, Alexei Navalny. It noted that the arrested suspect was an “active supporter” of Mr. Navalny’s group.

Shortly before the announcement, Russia’s Investigative Committee, the top state criminal investigation agency, reported the arrest of Darya Tryopova, a 26-year-old St. Petersburg resident suspected of involvement in the attack. Ms. Tryopova had been previously detained for taking part in anti-war rallies.

Like something out of a bad spy movie, the bomb was apparently hidden in a makeshift bust of the blogger that he was given as a gift just before the explosion.

According to Russian media reports, Ms. Tryopova told investigators that she was used as a carrier to deliver the explosive device, but didn’t know it was hidden in the bust.

Witnesses said that the suspect asked questions and exchanged remarks with Tatarsky during the discussion. One witness said the woman told Tatarsky that she had made a bust of the blogger but that guards asked her to leave it at the door, suspecting it could be a bomb. They joked and laughed, and then she went to the door, grabbed the bust, and presented it to Tatarsky.

A video showed Tatarsky making jokes about the bust and putting it on the table next to him just before the explosion, but video of the blast itself was only seen from outside the restaurant.

No one publicly claimed responsibility, but military bloggers and patriotic commentators immediately blamed Ukraine for the attack and compared the bombing to last August’s assassination of a nationalist television commentator, Darya Dugina, who was killed when a remotely controlled explosive device planted in her SUV blew up as she was driving on the outskirts of Moscow.

Russian authorities blamed Ukraine’s military intelligence for Dugina’s death, but Kyiv denied involvement.

Dugina’s father, Alexander Dugin, a nationalist philosopher and political theorist who strongly supports the invasion of Ukraine, hailed Tatarsky as an “immortal” hero who died to save the Russian people.

Reacting to Tatarsky’s death, Russia’s foreign ministry spokeswoman, Maria Zakharova, said late Sunday his activities “have won him the hatred of the Kyiv regime” and noted that he and other Russian military bloggers have long faced Ukrainian threats.

The Russian owner of the Wagner Group military contractor spearheading Moscow’s offensive in eastern Ukraine, Yevgeny Prigozhin, said he owned the cafe and handed it over to a patriotic group for meetings. He said he doubts the Ukrainian authorities’ involvement in the bombing, saying the attack was likely launched by a “group of radicals” unrelated to the government at Kyiv.

Since the fighting in Ukraine began February 24, 2022, Ukrainian authorities have refrained from claiming responsibility for various fires, explosions, and apparent assassinations in Russia. At the same time, officials in Kyiv have jubilantly greeted such events and insisted on Ukraine’s right to launch attacks in Russia.

A top Ukrainian government official cast the explosion that killed Tatarsky as part of internal turmoil. “Spiders are eating each other in a jar,” a Ukrainian presidential adviser, Mykhailo Podolyak, wrote in English on Twitter late Sunday. “Question of when domestic terrorism would become an instrument of internal political fight was a matter of time.”

Tatarsky, who had filed regular reports from Ukraine, was the pen name for Maxim Fomin, who had accumulated more than 560,000 followers on his Telegram messaging app channel.

Born in the Donbas, Ukraine’s industrial heartland, Tatarsky worked as a coal miner before starting a furniture business. When he ran into financial difficulties, he robbed a bank and was sentenced to prison. 

He fled from custody after a Russia-backed separatist rebellion engulfed the Donbas in 2014, weeks after Moscow’s annexation of Ukraine’s Crimean Peninsula. Then he joined separatist rebels and fought on the front line before turning to blogging.