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".
Timeline of events: Why was Navalny Putin's greatest antagonist
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.