Foreign Office officials have summoned the Russian Embassy amid anger in Western capitals over the death of jailed opposition leader Alexei Navalny.
Foreign Secretary Lord Cameron said Russian President Vladimir Putin must be held accountable, as he warned that there should be “consequences” for the Moscow leader, of whom Mr Navalny was one of the most prominent and persistent critics even while behind bars.
The Foreign Office said on Friday it has “summoned the Russian Embassy to make clear that we hold the Russian authorities fully responsible”.
Britain has joined other western countries in condemning the Kremlin after 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.
A Foreign Office spokesperson said Mr Navalny’s death must be “investigated fully and transparently”.
They said: “Alexei Navalny dedicated his life to exposing the corruption of the Russian system, calling for free and open politics, and holding the Kremlin to account.
“We stand today with his family, friends, colleagues and supporters. Our thoughts go out to them.
“The Russian authorities saw Mr Navalny as a threat. Many Russian citizens felt he gave them a voice.
“In recent years, the authorities imprisoned him on fabricated charges, poisoned him with a banned nerve agent, and sent him to an Arctic penal colony. No-one should doubt the brutal nature of the Russian system.”
It is understood officials were informed the Russian Ambassador was too ill to attend, with a deputy sent instead.
It came as a crowd of protesters gathered outside the Russian Embassy in central London in the wake of his death.
Lord Cameron, who was at the Munich Security Conference on Friday, told broadcasters: “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.”
Navalny was a hero to Russians and many others.
While some looked away, he spoke up about the lies and brutality of Putin’s regime.
They murdered him to silence him. His courage lives on in those who reject Moscow’s dictatorship.
— Tom Tugendhat (@TomTugendhat) February 16, 2024
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.
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, with tributes also coming from across British politics.
Liberal Democrat leader Sir Ed Davey said Mr Putin would “never kill the light of freedom democracy which Navalny has stood for so courageously”.
Bill Browder, the staunch Putin critic who has lobbied for sanctions against Russia since his associate Sergei Magnitsky died after exposing tax fraud involving Russian officials, said it was “demoralising” Putin can feel “untouchable”.
The widow of Alexander Litvinenko, the Russian defector to the UK who was poisoned and died in 2006, said his death was a “huge challenge for the West”.
“How many other murders and killings, prominent opposition people in Russia, in another part of the world, you will accept?” Marina Litvinenko asked on BBC Newsnight.
Asked about the timing of his death, she said: “It is about to show they can do anything they want.”
Mr Navalny had been moved in December from his former prison in the Vladimir region of central Russia to a “special regime” penal colony, the highest security level of prisons in Russia, above the Arctic Circle.
His allies decried the transfer to the town of Kharp, in the remote Yamalo-Nenets region notorious for its long and severe winters, as yet another attempt to silence him.
The opposition leader was convicted in 2013 of embezzlement, but later the prosecutor’s office surprisingly demanded his release pending appeal, after which a higher court gave him a suspended sentence.
Many observers attributed his release to a desire by authorities to add a tinge of legitimacy to the mayoral election in Moscow, in which he had registered as a candidate.
Mr Navalny ultimately finished second in the contest, which was seen as an impressive outcome, as the incumbent had the backing of Mr Putin’s political machine.
When the Russian president has spoken about Mr Navalny previously, he has made it a point not to mention the activist by name, referring to him only as “that person” or similar in an apparent effort to diminish his importance.
Mr Putin recently launched a presidential campaign for his fifth term in office.