Alexei Navalny: Daring opposition leader who died behind bars

He was for years the most prolific critic of President Vladimir Putin and his policies, returning to Russia after recovering from a near-fatal poisoning attack that his supporters say was orchestrated by the Kremlin.

He was immediately imprisoned on his arrival and on Friday could not be revived by medics when he lost consciousness after going for a walk, the prison service said.

During his time behind bars, the 47-year-old appeared in grainy videos from makeshift court hearings, daring to slam Putin over his offensive in Ukraine.

His message -- relayed to fans through social media content -- contrasted dramatically to that of Putin, a Soviet-styled, 71-year-old former KGB agent who has ruled for over 20 years.

"(Russia) is floundering in a pool of either mud or blood, with broken bones, with a poor and robbed population, and around it lie tens of thousands of people killed in the most stupid and senseless war of the 21st century," Navalny said in one statement.

His criticism, which resonated with thousands of young supporters, proved a source of irritation for a Kremlin that rights groups accused of wiping out dissent by any means necessary.

His death will only exacerbate these concerns.

- 'I am not afraid' -

In 2018, he had campaigned across the country to be president, published corruption investigations that embarrassed the Kremlin, and rallied massive crowds onto Russia's streets.

His return to Russia in January 2021 despite facing jail put him on a collision course with Putin, after Navalny blamed the poisoning attack in Siberia on the Kremlin.

"I'm not afraid and I call on you not to be afraid," he said in an appeal to supporters as he landed in Moscow, moments before being detained on charges linked to an old fraud conviction.

His arrest spurred some of the largest demonstrations Russia had seen in decades, and thousands were detained at rallies nationwide calling for his release.

Navalny's team countered Putin with the release of "Putin's Palace," an investigation into a lavish Black Sea mansion that his team claimed was gifted to Putin through corruption.

The expose forced a rare denial from Putin, who quipped that if his security services had really been behind the poisoning, they would have finished the job.

While Navalny trafficked confidently in memes, Putin is known both for not using the internet and asking a teenager who wanted him to follow his YouTube channel: "What should I sign?"

A similar Navalny corruption video targeting then Prime Minister Dmitry Medvedev spurred large demonstrations in 2017, with protesters carrying rubber ducks which became a symbol of the protests.

Ahead of a presidential election in 2018, Navalny toured cities across the country to drum up support but was barred from running because of the old fraud charge.

"(Putin) fears me and he fears the people I represent," he told AFP at the time.

Before that, he had challenged Sergei Sobyanin to become Moscow mayor and forced a runoff.

- 'Crooks and thieves' -

At rallies and in courtrooms, Navalny was a convincing public speaker and rallied protesters around home-grown slogans like "the party of crooks and thieves" to slam the ruling United Russia party.

But he was been tainted by an early foray into far-right nationalism, and a pro-gun video from 2007 routinely resurfaced in which he compared people from the ex-Soviet South Caucasus region to cockroaches.

Navalny also remains a fringe figure for a large portion of Russian society, who back the Kremlin's official portrayal of him as a Western stooge and convicted criminal.

He had become such a thorn in the Kremlin's side that Putin refused to pronounce his name in public. His anti-corruption group was shuttered and his top allies are either imprisoned or in exile.

- 'Cannot shut my mouth' -

Navalny's team said he had been harassed in prison and repeatedly moved to a punitive solitary confinement cell.

He said guards had subjected him and other inmates to "torture by Putin", making them listen to the president's speeches.

Still, Navalny was upbeat and sardonic on social media accounts curated by aides, even despite his condition.

The lawyer by training had fought for basic rights and taken prison officials to court. He had also tormented them, filing formal requests for a kimono and a balalaika -- a traditional musical instrument -- and to be allowed to keep a kangaroo.

"You cannot shut my mouth," he declared.