US President Joe Biden directly blamed Russian leader Vladimir Putin on Friday for the reported death of Alexei Navalny in prison, describing the Kremlin critic as a “powerful voice for the truth.”

Saying he was “outraged” by the news, Biden said he did not yet know exactly what had happened to Navalny, but that it was the fault of Putin and his “thugs.”

“Make no mistake, Putin is responsible for Navalny’s death. Putin is responsible,” Biden said in televised remarks from the White House.

“What has happened to Navalny is yet more proof of Putin’s brutality. No one should be fooled.”

Biden said he was “looking at options” on how to respond but did not go further.

Asked in 2021 after meeting Putin in Switzerland, what would happen were Navalny to die, Biden said: “I made it clear to him that I believe the consequences of that would be devastating for Russia.”

On Friday, Biden hailed Navalny’s achievements.

“Even in prison he was a powerful voice for the truth,” Biden said. “God bless Alexei Navalny, his courage will not be forgotten.”

Russian officials said Navalny died on Friday in an Arctic prison, a month before an election poised to extend Putin’s hold on power.

Navalny’s death after three years in detention and a poisoning that he blamed on the Kremlin deprives Russia’s opposition of its figurehead at a time of intense repression and Moscow’s invasion of Ukraine.