Russian investigators have detained a woman in their hunt for the killers of pro-war blogger Vladlen Tatarsky in a blast at a St Petersburg cafe.
In video released by authorities - most likely recorded under duress - Darya Trepova is heard admitting she handed over a statuette that later blew up.
But in the footage, she does not say she knew there would be an explosion, nor does she admit any further role.
Investigators said they had evidence the attack was organised from Ukraine.
However, Kyiv officials said it was a case of Russian infighting.
More than 30 people were wounded in the bombing in Russia's second city.
Tatarsky had been attending a patriotic meeting with supporters in the cafe as a guest speaker late on Sunday afternoon.
A video circulating on social media showed a young woman in a brown coat apparently entering the cafe with a cardboard box.
Images showed the box being placed on a table in the cafe before the woman sat down. Another video showed a statue being handed to Tatarsky.
In a brief excerpt of her interrogation released by the ministry, Darya Trepova, 26, appeared under duress as she sighed repeatedly.
When her interrogator asked if she knew why she was detained, she replied: "I would say for being at the scene of Vladlen Tatarsky's murder... I brought the statuette there which blew up."
Asked who gave it to her she responded: "Can I tell you later please?"
Russia's anti-terrorism committee alleged the "terror attack" was organised by Ukrainian special services "with people co-operating with" opposition leader Alexei Navalny.
The investigative committee later went further, saying it had evidence it was "planned and organised from Ukrainian territory". It was working to establish the "entire chain" of people involved, it added.
Navalny's Anti-Corruption Foundation, which has released a series of exposés of corruption involving the Putin entourage, said it was "very convenient" for the Kremlin to blame its critics when Navalny was due to go on trial soon for extremism.
Navalny has been in jail ever since he returned to Russia from Germany in January 2021. He survived a nerve agent attack in Russia in August 2020, which was blamed on Russian FSB security service agents.
Foundation head Ivan Zhdanov said everything pointed to FSB agents themselves. "Naturally we have nothing to do with this," he said, adding that Russia needed an external enemy in the form of Ukraine and a domestic one in Navalny's team.
Ms Trepova was detained in a St Petersburg flat owned by a friend of her husband's, Russian reports said.
On the day of Russia's full-scale invasion last year she was reportedly detained for a number of days for taking part in an anti-war protest.
The cafe, Street Food Bar No 1 near the River Neva, was once owned by Yevgeny Prigozhin - who runs Russia's notorious Wagner mercenary group which has taken part in much of the fighting in Bakhmut in eastern Ukraine.
Prigozhin said he had handed it over to Cyber Front Z, a group that calls itself "Russia's information troops" and said it had hired out the cafe for the evening.
Prigozhin paid tribute to Tatarsky, whose real name was Maxim Fomin, in a late-night video which he declared was filmed from the town hall in Bakhmut.
He displayed a flag which he said had the words "in good memory of Vladlen Tatarsky".
Tatarsky, a vocal supporter of Russia's war in Ukraine, was neither a Russian official nor a military officer. He was a well-known blogger with more than half a million followers and, like Prigozhin, had a criminal past.
Born in the Donetsk region of eastern Ukraine, he said he joined Russian-backed separatists when they released him from jail, where he was serving time for armed robbery.
He was part of a pro-Kremlin military blogger community that has taken on a relatively high-profile role since Russia's full-scale invasion of Ukraine began in February 2022.
Tatarsky is among those who have gone so far as to criticise the Russian authorities, slamming the military and even President Vladimir Putin for setbacks on the battlefield.
Unusually, Tatarsky took up arms in combat operations and reported from the front line. He claimed to have helped launch combat drones and build fortifications.
Last September, he posted a video inside the Kremlin where Mr Putin was proclaiming the annexation of four part-occupied Ukrainian regions.
"We will defeat everyone, we will kill everyone, we will rob everyone as necessary. Just as we like it," Tatarsky told his followers.
The military bloggers have provided information about the war in a country where many have become frustrated with the lack of accurate information from official sources.
Information provided by the Russian military, Kremlin-controlled television and state officials has been criticised for being inaccurate.
Last week, several official Russian sources shared a video allegedly showing Ukrainian troops harassing civilians. Western analysts proved using open-source information that the video had been staged.
Some pro-Kremlin bloggers also slammed the video as a crude fake. Much of the bloggers' pro-Russian material is not factual either.
Who was behind Tatarsky's murder is unclear, but it is reminiscent of the killing of Darya Dugina, a vocal supporter of the war and the daughter of a Russian ultra-nationalist. She died in a car bomb attack near Moscow last August.
While Russian officials pinned the blame firmly on Ukraine, in Kyiv presidential adviser Mykhailo Podolyak said the blast was part of a Russian "internal political fight", tweeting: "Spiders are eating each other in a jar."
The Ukrainians have proved themselves as more than capable of carrying out drone attacks and explosions deep inside Russian territory in recent months. They rarely admit involvement but often drop hints.
Yevgeny Prigozhin said he did not think it was the Ukrainian government: "I think there is a group of radicals operating, which unlikely has something to do with the government."
The blast could be linked to Russian political infighting. There are now a lot of angry men carrying guns in Russia.
With the military running low on troops, convicts have been let out of prison, handed weapons and sent to the front. Russian authorities have also conducted large-scale recruitment campaigns for volunteer fighters and recruited some 300,000 men in a "partial mobilisation".
The Kommersant newspaper recently reported that the number of murders committed in Russia last year rose for the first time in 20 years.
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