Igor Girkin was the top military commander of the self-proclaimed 'Donetsk People's Republic' in Ukraine
Igor Girkin was the top military commander of the self-proclaimed 'Donetsk People's Republic' in Ukraine AFP

former top commander of Russian-backed rebels in eastern Ukraine, Igor Girkin, went on trial in Moscow on Thursday on charges of extremism for criticising the Kremlin's military strategy towards Kyiv.

The 52-year-old hardline nationalist -- better known by his alias Igor Strelkov -- was instrumental in sparking hostilities in 2014 between Kremlin proxies in neighbouring Ukraine and that country's national army.

But he fell foul of Moscow and was detained after the Wagner mercenary group -- a key force fighting in Ukraine for the Kremlin -- tried to topple Russia's military leadership in June.

Girkin was detained in July following a series of social media posts critical of Russian President Vladimir Putin that went out to hundreds of thousands of followers.

The case against Girkin, who became an outspoken blogger, has illustrated how any criticism of the military is off-limits, even from ardent Russian nationalists who support the conflict.

The hearing, held behind closed doors, began in Moscow on Thursday according to social media accounts curated by his supporters.

Girkin, who has declared his intention of challenging Putin in the presidential election next March, faces up to five years in prison.

Supporters have said the case against him is politically motivated.

Girkin has had many lives.

He was one of the pivotal figures in the pro-Kremlin insurgency that erupted in eastern Ukraine in 2014.

When Sloviansk in eastern Ukraine became a rebel stronghold, he ruled it with an iron fist, reportedly authorising executions for petty theft.

But he was squeezed out of the separatist leadership later that year under mysterious circumstances and returned to Russia, where he lost all influence, until the Kremlin-s fully-fledged assault on Ukraine began in February 2022.

That same year, he was sentenced in absentia to life imprisonment by a Dutch court over the downing of Malaysia Airlines passenger flight MH17 over Ukraine in 2014, which killed all 298 on board.

Girkin returned to the spotlight after the Russian military offensive in Ukraine started, becoming one of the most vocal critics of Putin and of the way in which the offensive has been conducted.

Even after his arrest, Girkin -- who sports a moustache in the style of a Tsarist officer -- continued his criticism online.

In August he said he wanted to run in the presidential elections next year.

"I consider myself more competent in military affairs than the incumbent president and certainly more competent than the defence minister," he said when he announced his candidacy.

And he piled up criticism of Putin, saying the Russian leader "had been led by the nose" by both international leaders and national allies.

Unlike Putin, Girkin said he "would not have to give in to the wishes of my friends to the detriment of Russia's economy", referring to numerous allegations of corruption.