Hundreds gather outside Russian Embassy in London
Hundreds of people gathered outside the Russian Embassy in London following the death of jailed opposition leader Alexei Navalny.
Ahead of a demo they laid flowers, lit candles and held placards calling for the Kremlin to be held accountable.
They chanted 'We are Navalny' and 'Don't give up.'
Russia's federal prison service said in a statement that the 47-year-old politician and anti-corruption campaigner had died.
According to the agency, he became unwell after a walk on Friday and lost consciousness.
An ambulance arrived, but he died despite attempts to resuscitate him, it said.
Speaking to broadcasters as he attends the Munich Security Conference on Friday, Lord Cameron said: "We should hold Putin accountable for this, and no-one should be in any doubt about the dreadful nature of Putin's regime in Russia after what has just happened."
Asked whether there should be consequences, he said: "There should be consequences because there's no doubt in my mind that this man was a brave fighter against corruption, for justice, for democracy, and look what Putin's Russia did to him.
"They trumped up charges, they imprisoned him, they poisoned him, they sent him to an Arctic penal colony, and he's died, and that is because of the action that Putin's Russia took."
In an earlier post on X, formerly Twitter, Rishi Sunak described Mr Navalny as "the fiercest advocate for Russian democracy" who had "demonstrated incredible courage throughout his life".
"My thoughts are with his wife and the people of Russia, for whom this is a huge tragedy," the Prime Minister said.
Security minister Tom Tugendhat went a step further, accusing Mr Putin's regime of having murdered Mr Navalny in order to silence him.
Mr Navalny, who campaigned against official corruption and organised major anti-government protests, has been behind bars since January 2021.
He was arrested on his return from Germany, where he had been recuperating after a nerve agent poisoning that he blamed on the Kremlin, on charges he dismissed as part of a politically motivated vendetta.
Since the start of his imprisonment, the opposition leader had remained a thorn in the side of Mr Putin via scathing attacks that his associates continued to post on social media.
Kremlin spokesman Dmitry Peskov said Mr Putin was informed of Mr Navalny's death and the prison service was looking into the matter in line with standard procedures.
Mr Navalny's spokeswoman Kira Yarmysh said on X that the politician's team had no confirmation of his death so far and that his lawyer was travelling to the town where he was held.
His widow, Yulia Navalnaya, has called on the international community to unite in holding the "terrible" and "evil" regime in Moscow responsible in the wake of the news.
Several world leaders and Putin critics placed the blame squarely on the shoulders of the Russian president and his government on Friday.
Speaking in Munich, US vice president Kamala Harris said: "Russia is responsible and we will have more to say about this later."
Ukrainian President Volodymyr Zelensky said "it is obvious that he was killed by Putin" as he visited Germany.
German Chancellor Olaf Scholz said Mr Navalny's death makes clear "what kind of regime this is" and that he had "probably now paid for (his) courage with his life".
Former prime minister Boris Johnson echoed those remarks: "No one can be in any doubt that Alexei Navalny has been put to death by Vladimir Putin."
Tributes came from across British politics in the UK on Friday, with Labour leader Sir Keir Starmer calling his death "terrible news for the Russian people".
Liberal Democrat leader Sir Ed Davey said Mr Putin would "never kill the light of freedom democracy which Navalny has stood for so courageously".
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