(CN) — Alexei Navalny, an opposition leader and fierce critic of Russian President Vladimir Putin, has died while serving a long sentence in a prison in the Arctic Circle, Russian prison officials said Friday.
His death was condemned by Western leaders as a political assassination carried out by Putin's regime ahead of March presidential elections.
“Make no mistake. Putin is responsible for Navalny’s death,” said U.S. President Joe Biden at a White House news conference. “What has happened and evolving is yet more proof of Putin’s brutality. No one should be fooled, not in Russia, not at home, not anywhere in the world.”
Asked if his death was an assassination, Biden replied that “there is no doubt that the death of Navalny is a consequence of something Putin and his thugs did.”
U.S. Secretary of State Antony Blinken accused the Kremlin of having “persecuted, poisoned and imprisoned” the Putin critic for years.
“The fear of one man only underscores the weakness and rot at the heart of the system that Putin has built,” Blinken added.
“He was slowly murdered by President Putin and his regime, who fear nothing more than dissent from their own people,” European Union Commission President Ursula von der Leyen said in a statement.
Washington and Brussels vowed to hold Russian officials accountable for Navalny's death, though they did not specify what actions they might take. Von der Leyen called on Moscow to release all political prisoners. Western leaders also called for an investigation into the activist's death.
Biden said that even though Russia already has been “subjected to great sanctions across the board."
"We’re contemplating what else can be done," he said. "We’re looking at a whole number of options.”
Moscow accused Western leaders of wrongly jumping to conclusions about Navalny's death.
“The death of a person is always a tragedy,” Russia's foreign ministry said. “Instead of sweeping accusations, one ought to show restraint and wait for the official results of the forensic medical examination.”
Navalny, 47, was barred from running in the March election because of a criminal conviction — but he nonetheless had been urging Russians to protest against the Putin regime and the Ukraine war. Putin, Russia's longest-serving leader since Joseph Stalin, is expected to win reelection.
Russia's Federal Prison Service said Navalny felt unwell after a walk on Friday and lost consciousness.
“The medical staff of the institution arrived immediately, and an ambulance team was called,” prison officials said. “All necessary resuscitation measures were carried out, which did not yield positive results.”
The cause of death was under investigation, prison officials said. The Kremlin said it did not know the cause of his death. Dmitry Peskov, the Kremlin spokesman, said he was unsure if Navalny had died from a blood clot, as reported by Russian media. “I don't know. Doctors will find out,” he said, as reported by Russian news agencies.
In recent social media posts and a court video taken Thursday, Navalny showed no signs of illness and appeared upbeat.
Navaly's spokeswoman, Kira Yarmysh, said relatives and lawyers would travel Saturday to the Siberian prison to confirm his death.
Still, she said reports of his death were “most likely true," since the Kremlin had commented on it.
Yulia Navalnaya, Navalny’s wife, was in Germany for the Munich Security Conference when news of his death was announced. She took the stage at the high-profile security summit and spoke to the assembly of world leaders, military chiefs and diplomats.
“I thought, ‘Should I stand here before you or should I go back to my children?' And then I thought, ‘What would have Alexei done in my place?' And I’m sure that he would have been standing here on this stage,” she said.
Follow @cainburdeau
