"I don’t know whether I should believe this horrible news or not," Navalny's wife has said.

Speaking at the Munich Security Conference, Yulia Navalnaya said the news of her husband's death so far only came from state sources.

"We can't really believe Putin and his government," she says.

She then adds that if news of her husband's death is true, Putin and his allies should bear personal responsibility for it and everything "they are doing to Russia".

"I am asking everyone who is here to unite and help punish the Russian regime," Navalnaya says.

Jen Monaghan
BBC Monitoring

While Navalny may be a trending topic on social media, Russian state TV channels have made little to no mention of his death.

Despite authorities announcing the news this morning, Russia's most popular TV channel Rossiya 1 failed to include the news in its bulletin.

It was approximately 45 minutes before Russia's second-most popular network, Channel One, reported the news, with host Vyacheslav Nikonov reading out the statement released by prison authorities at the end of the programme.

Most of the reports have failed to provide viewers with any context about who Navalny was or why he was in prison.

Steve Rosenberg
BBC Russia editor, in Moscow

The Russian prison service issued a brief statement, and according to that statement, its version of events, Alexei Navalny fell ill this morning after a walk inside the penal colony.

The Russian prison service claims that he lost consciousness almost immediately, and that local medical staff, prison medical staff, were called to the scene and then an ambulance was called.

Attempts were made, again according to the prison service, to revive him, but those attempts failed.

His cause of death as yet unknown, according to the official version of events.

Alexei Navalny was the Kremlin's most vocal critic. No doubt about that.

In fact, he was the only opposition leader in this country who had been capable of bringing large numbers of people, large numbers of protesters onto the streets across the country.

He got under the Kremlin's skin for sure and had accused them of trying to assassinate him back in 2020.

Alexei Navalny's mother Lyudmila says her son was "alive, healthy and happy" when she last saw him on 12 February, in a Facebook post quoted by Novaya Gazeta newspaper.

"I don't want to hear any condolences," she adds.

Image source, EPA

US Secretary of State Antony Blinken has said that if Navalny's death is confirmed, it "only underscores the weakness and rot at the heart of the system that Putin has built."

"First and foremost, if these reports are accurate, our hearts go out to his wife and his family," he says at the Munich security conference, adding that "Russia is responsible" if the death is confirmed.

Asked about Navalny's death this morning on NPR, US National Security Advisor Jake Sullivan says the US is trying to confirm exactly what happened.

"It is a terrible tragedy, and given the Russian government's long and sordid history of doing harm to its opponents, it raises real and obvious questions about what happened here," he tells the US broadcaster.

"But I'll withhold further comments on it until we learn more and we are actively seeking confirmation, as I know Mr. Navalny's family is as well. And we'll determine from there what – what comes next."

Image source, Reuters

2007 - Owing to his savvy use of social media in the form of a blog, Alexei Navalny gains prominence by documenting his investment in state-owned oil companies, in search of evidence of corruption.

Shortly after, he was expelled from liberal opposition party Yabloko for taking part in 'nationalist activities'.

December 2011- Alexei's Anti-Corruption foundation has amassed a sizeable following exposing the riches of Kremlin elites. Later that year, he becomes a key leader of election protest after Putin's United Russia party wins the vote despite the Kremlin's campaign being marred by allegations of fraud.

July 2013 - Navalny is arrested on embezzlement charges; accused by the Russian government of fraud amounting to 16 million rubles ($500,000). He denies the charges.

September 2013 - A bid to become Moscow's mayor, sees Navalny finish in second place with strong support to Kremlin backed Sergei Sobyanin.

December 2018 - Five years later, Navalny's presence continues to disrupt Putin's idealised Russia as he attempts to run for president. However, Putin bans his run, citing Navalny's embezzlement conviction. Despite Navalny urging Russian's to boycott the vote, Putin goes on to win a fourth term.

August 2020 - Navalny is hospitalised in Siberia and placed in a medically induced coma after losing consciousness during a flight. Tests show he was poisoned by Novichok, a nerve agent commonly used in the Soviet era. The Kremlin denies being responsible for the attack.

January 2021 - Returning to Moscow, Navalny is detained at the airport. Thousands of people demonstrate across Russia for his release.

February 2021 - Alexei is handed a two-and-a-half-year sentence for breaching the conditions of a suspended sentence while recuperating in Germany. He is sent to a penal colony.

August 2023 - Navalny's sentence is increased to nine years after a conviction on new charges of embezzlement and contempt of court. An additional 19 years at a "special regime" facility are added on charges of extremism.

December 2023 - After going missing for two weeks, the opposition leader is located in a penal colony in the North Arctic.

February 2024 - Alexei Navalny dies in prison.

Alexei Navalny managed to communicate with the world through his lawyers, giving them messages which his team would then post online.

The last post on his Instagram, external came just two days ago, on 14 February. It was a Valentine's day message addressed to Navalny's wife, Yulia, with a photo of the couple.

"Between us there are cities [and] thousands of kilometres," the post reads. "But I feel that you are near every second, and I love you more and more."

Image source, Instagram/@navalny

Sarah Rainsford
BBC Eastern Europe Correspondent

When Navalny survived the attempt to kill him with a nerve agent, Novichok, he knew he would never be safe again in Russia.

And yet, after he recovered in Germany from the poisoning, he flew home.

As a Russian politician, he could not contemplate the life of a political émigré, increasingly out of touch and irrelevant.

He said he had to be in Russia, whatever the risk.

But the risk was huge.

Navalny was arrested as soon as he landed in Moscow, in January 2021, and has been locked up ever since.

He would appear via video link from prison, periodically, for hearings in the multiple criminal cases against him – all excuses to keep him behind bars.

He was gaunt. His head shaven, and his prison uniform loose. But he would sound as defiant as ever.

Navalny never abandoned his hope and belief in what his team called "the beautiful Russia of the future" – the end of Putin’s long and repressive rule and the prospect of political change in his country.

But since the activist’s arrest, Putin has launched a war on Ukraine, Navalny’s own political organisation has been banned as "extremist", his team members arrested, and all well-known critics of Putin have fled the country - or been imprisoned.

Today, those prisoners’ families, too, must be terrified.

For them, and for all those who imagined a different Russia, the outlook has never been so bleak.

The spokeswoman for Russia's foreign ministry, Maria Zakharova says "Western allegations" about the death of Navalny are "self-revealing".

In a statement on Telegram, she says the results of the forensic analysis of the cause of Navalny's death are currently unavailable.

Zakharova adds that she believes the West has already come to its own conclusions.

We're continuing to get some reaction from across the world to the death of Alexei Navalny.

Jens Stoltenberg, the secretary-general of NATO, says he is "saddened and disturbed by reports coming form Russia".

Navalny's death is "terrible news" says UK prime minister Rishi Sunak, who says he "demonstrated incredible courage throughout his life".

German Chanceller Olaf Scholz says the activist "paid for his courage with his life".

While Czech Foreign Minister Jan Lipavsky has called on the world to "honour the memory" of a man "imprisoned and tortured to death for standing up to Putin"

And Krisjanis Karins - former Latvian prime minister and current foreign minister - says he is "deeply distraught" by the news and says his "death is fully on the conscience of Putin’s criminal regime".

European Council President Charles Michel has said the bloc considers the Russian regime to bear "sole responsibility" for Navalny's "tragic death".

In a post on X, Michel said Navalny "fought for the values of freedom and democracy" and made the "ultimate sacrifice" for his ideals.

"I extend my deepest condolences to his family. And to those who fight for democracy around the world in the darkest conditions. Fighters die. But the fight for freedom never ends," Michel added.

Image source, EPA

Russian President Vladimir Putin has been informed of Navalny's death, according to Kremlin spokesman, Dmitry Peskov.

Peskov also said on Friday that Russia's penitentiary service was making "all checks" regarding Navalny's death but that he had no other information about the matter.

Navalny has been in jail since 2021, and in December he was moved to an arctic penal colony in Siberia.

Charges against Navalny, one of Vladimir Putin's most vociferous critics, are widely seen as politically motivated.

He was originally sentenced to three-and-a-half-years for violating the conditions of a suspended sentence in an embezzlement case.

In February 2022, he was put on trial again. This time it was alleged he stole $4.7m (£3.5m) of donations given to his political organisations.

"You're going to increase my term indefinitely. What can we do about it?" Navalny said during the court hearing.

He was found guilty, and ordered to spend nine years in a "strict regime penal colony".

And in August last year, this jail term was extended to 19 years after he was found guilty of founding and funding an extremist organisation - charges he has denied.

Reaction to the news of Russian political activist Alexei Navalny's death is flowing in now.

In a post on X (formerly known as Twitter), French Foreign Minister Stéphane Séjourné says that Navalny "paid with his life" for his "resistance to Russian oppression".

"His death in a penal colony reminds us of the reality of Vladimir Putin's regime," he adds.

Kira Yarmysh, Navalny's spokesperson, said that they don't have any confirmation of his death yet.

In a post on X (formerly Twitter), she writes, external: "The Federal Penitentiary Service in the Yamalo-Nenets District is disseminating news about the death of Alexei Navalny in IK-3. We don't have any confirmation of this yet."

Navalny's lawyer is now flying to Siberia and his team will report more information as they have it, she adds.

As we reported moments ago, Navalny was seen in a video call in January, joking about his prison outfit at the Arctic penal colony he had been moved to a month earlier.

The IK-3 colony, nicknamed "Polar Wolf", is in the northern town of Kharp, some 1,900km (1,200 miles) north-east of Moscow.

It's seen as one of the toughest jails in Russia and most detainees held there have been convicted of serious crimes.

Speaking to journalists on the video call, Navalny appeared to be in good spirits, joking that he was yet to receive any Christmas mail, due to being "quite far away".

More now from the prison service in the Yamalo-Nenets district, where Navalny had been serving his sentence.

In a statement, it said he had "felt unwell" after a walk on Friday.

He had "almost immediately lost consciousness", it continued, adding that an emergency medical team had immediately been called and tried to resuscitate him but without success.

"The emergency doctors declared the prisoner dead. Cause of death is being established."

Navalny's lawyer Leonid Solovyov told Russian media he would not be commenting yet.

Alexei Navalny was probably Putin’s most famous critic.

For more than a decade, he exposed corruption at the heart of Russian power. His video investigations have received tens of millions of views online

A charismatic campaigner, Navalny, set up a network of regional campaign offices, having planned to run for president in 2018. He was barred from the vote.

In 2020, he was poisoned in Siberia by what Western laboratories later confirmed to be a nerve agent.

He was treated abroad and had been jailed since returning to Russia in January 2021, when he was immediately arrested.

Before he was jailed he lived in Moscow with his wife Yulia and their two children.

Image source, Reuters

Russian opposition politician Alexei Navalny has died in prison, according to Russian authorities.

The ardent critic of President Vladimir Putin has been jailed since 2021.

In December, he was moved to a notorious artic penal colony, thousands of miles to the north-east of Moscow in Siberia.

A reason has not yet been given for his death, though prison authorities have said he felt unwell after a walk on Friday and then fell unconscious.

Navalny, who campaigned against what he described as rampant corruption within Russia, was poisoned in 2020 in what Western laboratories later confirmed to be a nerve agent.

In his last public appearance from prison on 10 January, Navalny joked that he that he was yet to receive any Christmas mail, due to being "quite far away".

Stay with us for live updates and reaction.