Russian authorities detained the ultra-nationalist Kremlin critic Igor Girkin on Friday on charges of inciting extremist activity.

Girkin, 52, made a name for himself as a separatist commander in eastern Ukraine during Russia's illegal annexation of the Ukrainian peninsula of Crimea in 2014. 

However, he has expressed sharp criticism of the Kremlin following Russia's full-scale invasion of Ukraine last year.

His wife wrote on his Telegram channel that Russia's Federal Investigative Committee (FSB) had come to their house and that "they took my husband out by his arms and in an unknown direction."

The FSB asked a Moscow court to hold Girkin on charges of inciting extremism. He could be facing up to five years in prison if found guilty.

Girkin's sharp criticism of Putin

Earlier this year, Girkin, who is also known by his alias Igor Strelkov, said he would enter politics. And earlier this week, he posted a scathing rant apparently aimed at Russian President Putin, although he never directly named the politician.

On Tuesday, Girken wrote on Telegram that Russia has been led by a "failure" for 23 years — about the amount of time Russian President Vladimir Putin has been in power, in one form or another.

His detention comes in the aftermath of a short-lived rebellion of the mercenary group Wagner, led by mercenary chief Yevgeny Prigozhin , who has also heavily criticized Russia's military leadership. Girkin, who has over 875,000 subscribers on his messaging app, has also described Russia's military leadership as incompetent.

However, he recently described Prigozhin's action as treasonous and a major threat to the Russian state. 

At the same time, he has also accused Putin of incompetence since the invasion of Ukraine. 

"A lot of empty talk, the minimum of action and the utter lack of responsibility for failures —  that is Putin's style of late," Girkin said recently.

Girkin served in the Russian military during the Chechen separatist wars and later joined Moscow's Federal Security service.

Last year, a Dutch court convicted him and two other men of murder for their role in shooting down a Malaysia Airlines passenger jet with a Russian surface-to-air missile, which killed all 298 people on board.  

ab,ara/wmr (AP, Reuters, AFP, dpa )