Considered the leader of Russia's disparate opposition, Mr Navalny spent years crusading against Vladimir Putin's regime and the corruption he said was at its heart.

Languishing in prison on charges he said were politically motivated, the reaction to his death has been one of shock, but not surprise.

Follow latest: Reaction after Alexei Navalny dies

With its highest profile leader now dead, what remains of the opposition in Russia?

Will we see street protests and the ascent of presidential candidate Boris Nadezhdin to unite those opposed to Mr Putin's rule?

Sky News spoke to experts on Russian politics to see what we should expect in the coming days.

What did Alexei Navalny represent for the Russian opposition movement?

The last few years have been a story of an increasing crackdown on opposition inside Russia, particularly following the 2022 invasion of Ukraine.

The most active opposition is now outside Russia, says Dr Ben Noble, associate professor of Russian politics at University College London.

"Navalny served as a symbol of a difference in a political system that censors so much around Vladimir Putin," he said.

"Navalny criticised Putin but he also, with his team, constructed a vision of a different type of Russia."

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Military analyst Professor Michael Clarke said Mr Navalny was "the most credible opposition character in Russia", adding that he had a big movement behind him that was still active while he was in prison.

But he also highlighted that Mr Navalny was "not as liberal as people in the West would like to believe" and had a "rather Russian imperialist view" on foreign policy matters.

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What will happen now?

Opposition inside Russia is "very fragmented", Dr Noble says.

"I imagine we can expect to see some type of solidarity in shock, horror and outrage following his death."

But Dr Noble said he would not expect mass street protests in Russia, where Mr Navalny's name has been maligned for many years and where freedom of expression is extremely limited.

Team Navalny, based in Lithuania, will try and coordinate activities, Dr Noble added, which will become clearer in the next few days.

Samantha de Bendern, associate fellow at the Chatham House think tank, said no death of a prominent Russian opposition figure has resulted in protests.

But she added: "The context today is different: Russia is at war in Ukraine, and a new opposition candidate, Boris Nadezhdin, has created an embryonic anti-war movement hungry for change in Russia."

Boris Nadezhdin: A successor to Alexei Navalny?

There isn't an obvious candidate for Navalny 2.0, Dr Noble says.

"That speaks to the efficiency, the ruthlessness with which the political authorities in Russia, the Kremlin, have scorched the landscape of credible opposition to Vladimir Putin."

The Russian elections are coming up next month and President Putin is certain to win, Dr Noble says.

Boris Nadezhdin, the 60-year-old politician who has attempted to run against Mr Putin in the upcoming elections, is perhaps now the highest profile opposition figure inside Russia.

He has called for a halt to the war in Ukraine and urged Russia to start a dialogue with the West.

But he has been banned from standing by the Central Election Commission.

"An optimistic view is that Navalny's death may inject a new life into Nadezhdin... and give birth to a real movement," Ms de Bendern said.

"A pessimistic view would see Nadezhdin being silenced, either out of fear or more radical and potentially permanent methods."

Dr Noble said the Kremlin initially tolerated Nadezhdin, but when it saw the long lines of people turning out to endorse his candidacy it got "spooked".

"I think now they will be even more attentive to the prospect of Nadezhdin being another point of uncertainty in a system that increasingly does not tolerate uncertainty and opposition."

He added: "I don't think we should be expecting Nadezhdin to try and take on Navalny's mantle, mainly because the authorities just won't allow that."