Prominent Russian nationalist Igor Girkin, who has publicly accused President Vladimir Putin and army leaders of not prosecuting the war in Ukraine harshly or effectively enough, has been arrested and remanded in custody on charges of inciting extremism.
His detention in Moscow by his former employer, the FSB state security service, suggests authorities have wearied of his criticism of what they call Russia's "special military operation".
It follows an abortive mutiny last month led by another outspoken critic, Yevgeny Prigozhin, boss of the Wagner mercenary force, who is still free but has sharply curtailed his own verbal attacks.
The charge brought by FSB prosecutors carries a maximum sentence of five years in prison, state news agencies TASS and RIA Novosti reported.
The RBC news site said the Meshchansky district court in Moscow had remanded Mr Girkin in investigative custody until 18 September.
The 52-year-old, a former battlefield commander also known as Igor Strelkov, helped Russia annex Crimea from Ukraine in 2014 and then organise pro-Russian militias who wrested part of eastern Ukraine out of Kyiv's control.
He was handed a life sentence in absentia by a Dutch court in 2022 for his alleged role in the shooting down of Malaysia Airlines flight MH17 over eastern Ukraine in 2014, with the loss of 298 passengers and crew.
In footage from the court posted by the Telegram channel Shot, often one of the first to air official footage, Mr Girkin stood almost motionless in a glass cage, with his arms folded, staring straight ahead.
He had been regarded by many as untouchable due to his history and ties to the authorities, but had become more outspoken in recent months.
Mr Girkin announced in May that he and others had set up the 'Club of Angry Patriots' to enter politics to save Russia from what he said was the danger of turmoil due to military failures in Ukraine.
Asked at the time if he was naive to think he could launch a political movement without the assent of the Kremlin, he said: "I hope you would not call me a naive person."
Girkin urged Putin to hand over to 'someone capable'
In one of his most outspoken tirades on 18 July, in a post on his official Telegram channel, read by over 760,000 people, Mr Girkin personally insulted President Putin and urged him to transfer power "to someone truly capable and responsible".
In a message posted on Mr Girkin's official Telegram account, his wife, Miroslava Reginskaya, said: "Today, at about 11.30am, representatives of the Investigative Committee came to our house. I was not at home. Soon, according to the concierge, they took my husband out by his arms and in an unknown direction."
"I do not know anything about my husband's whereabouts, he has not contacted me."
RBC, citing two unnamed law enforcement sources, said his Moscow home had been searched and that he had been detained over a complaint against him made by a former Wagner employee.
Tatiana Stanovaya, founder of the R.Politik analysis firm, said the men who run Russia's law enforcement and power ministries had long wanted to arrest Mr Girkin.
"Strelkov (Girkin) had overstepped all conceivable boundaries a long time ago," she said.
"This is a direct outcome of Prigozhin's mutiny: the army's command now wields greater political leverage to quash its opponents in the public sphere."
Ms Stanovaya said Mr Girkin's detention was a signal that any of the bitterest critics of Russia's approach to the war could face prosecution.
