(Bloomberg) -- US President Joe Biden blamed Vladimir Putin for the prison death of Russian activist Alexey Navalny, joining a number of other western leaders holding the Kremlin responsible for the deal of its most prominent domestic political opponent.

Read More: Why Alexey Navalny Was Putin’s Domestic Enemy No. 1

“Putin is responsible. What has happened to Navalny is yet more proof of Putin’s brutality,” Biden told reporters at the White House Friday. “He was so many things that Putin is not - he was brave, he was principled, he was dedicated to building a Russia where the rule of law existed.”

Navalny lost consciousness after feeling unwell on returning from a walk and medical services were unable to revive him, Russian prison authorities said in a statement Friday. Officials were attempting to establish the cause of death, according to the statement. 

Navalny, 47, was declared dead at the start of official campaigning for the March 17 presidential election, in which Putin is likely to secure a fifth term.

Biden stopped short of announcing any new measures to punish Russia, saying only that “we’re looking at a whole number of options.”

The opposition leader’s wife, Yulia Navalnaya, addressed the Munich Security Conference shortly after learning of his death. “I do not know whether or not to believe this terrible news,” she said, after a standing ovation from the audience. “This regime and Vladimir Putin must bear personal responsibility for all those horrible things which they do to my country, our country.”

US Vice President Kamala Harris, who spoke earlier Friday at the conference, expressed her “sorrow and outrage” over the death in a private meeting with Navalnaya, the White House said.

Kremlin spokesman Dmitry Peskov said earlier Friday Putin had been informed of Navalny’s death. Peskov later condemned statements from Western leaders in response to the event as “absolutely unacceptable,” according to the state-run Tass news service. 

Read More: Why Alexey Navalny Was Putin’s Domestic Enemy No. 1: QuickTake

Navalny’s lawyer was on his way to Kharp, the site of the Arctic prison colony, but hadn’t received confirmation of his death yet, the opposition leader’s spokesperson, Kira Yarmysh, said on the X social media platform.

Read more: Why Alexey Navalny Was Putin’s Domestic Enemy No. 1: QuickTake

German Chancellor Olaf Scholz described news of the death as “very depressing” and offered his condolences to Navalny’s family.

Speaking in Berlin alongside Ukrainian President Volodymyr Zelenskiy, Scholz said Navalny’s fate “shows what kind of regime is in charge in Russia,” where anyone who expresses an opinion or criticizes the government “must fear for his or her life.” 

Zelenskiy directly accused his Russian counterpart. “It is obvious Navalny was killed by Putin,” he said. “Putin doesn’t care who will die for him to keep his post.”

Others in Ukraine were more critical of the Russian activist, however. His nationalist views, including accepting that the illegally annexed Crimea wouldn’t be returned, angered many Ukrainians.

European Council President Charles Michel said the bloc holds “the Russian regime” solely responsible for the activist’s death.

“For more than a decade, the Russian government and Putin personally persecuted, poisoned and imprisoned Alexey Navalny,” US Secretary of State Antony Blinken said in Munich, indicating Washington was still seeking confirmation of the news. “His death in a Russian prison and the fixation and fear of one man only underscores the weakness and rot at the heart of the system that Putin has built. Russia is responsible for this.” 

Blinken also met with Navalnaya at the conference, State Department spokesman Matthew Miller said.

While the European Union has already sanctioned many people connected to the Kremlin, the bloc will discuss whether others need to be added after Navalny’s death, a senior official said. 

Russia’s Foreign Ministry said the reactions of Western leaders amounted to a “blame Russia in any situation” plan in a statement on Telegram. The Moscow prosecutor’s office warned people against joining illegal protests in the Russian capital, Tass reported. 

Putin had always refused to call Navalny by his name in an effort to belittle the man he dismissed as a “blogger,” but who’d gathered widespread support for his attempts to expose corruption and seek public office.

Navalny was barred from running in the 2018 presidential election. Months before Putin ordered the 2022 invasion of Ukraine, Navalny’s nationwide network of opposition political activists was declared “extremist” and ordered to disband.

In August 2020, Navalny barely survived a nerve-agent attack that he and Western governments blamed on Putin’s secret service. After being treated in Germany — and despite near certainty he would be jailed — he returned to Russia in January 2021 and was immediately detained. He was eventually sentenced to a nine-year term for fraud and contempt of court.

Navalny was sentenced to an additional 19 years in August after a court convicted him of “extremism” in a trial held inside a high-security prison. 

The US and the EU had called for Navalny’s release, condemning his convictions as politically motivated.

Read more: Alexey Navalny, Corruption Fighter Who Defied Putin, Dies at 47

In prison, Navalny reported worsening health problems and blamed the authorities for denying him proper medical care. 

His health concerns deteriorated in August 2022, as prison authorities repeatedly placed him in a punishment cell for minor infractions of the rules. His allies accused the authorities of slowly poisoning him, perhaps through prison food, causing him to lose weight rapidly.

In December, just as Putin was preparing to announce his candidacy, Navalny was transferred to the remote prison camp, IK-3, in Russia’s Yamal-Nenets region, after nearly three weeks in which his whereabouts were unknown to his allies and lawyers. The settlement is about 3,300 kilometers (2,050 miles) by road from Navalny’s previous jail, which was about 100 kilometers outside Moscow.

“For those who still believe in elections in Russia, the killing of Navalny must be a final signal,” Lithuanian Foreign Minister Gabrielius Landsbergis said. “The West must not recognize elections in Russia and to sanction people who contributed to Navalny’s fate.”

--With assistance from Olesia Safronova, Courtney McBride, Michael Nienaber, Daryna Krasnolutska, Natalia Drozdiak and Josh Wingrove.

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