Russian opposition leader Alexei Navalny has died, according to a statement from Russia's prison service.

The big picture: Navalny, 47, was imprisoned after exposing corruption in Vladimir Putin's inner circle and forming the most effective political movement opposing the Russian leader. His death, if confirmed, has happened in the custody of the Russian state that persecuted him relentlessly.

• The Russian penitentiary service said Navalny lost consciousness while walking in the Arctic penal colony to which he was relocated in December.
• A spokesperson for Navalny, Kira Yarmysh, said on X that she did not have confirmation of Navalny's death. "As soon as we have some information, we will report on it."
• Putin's spokesperson, Dmitry Peskov, said reports of the death had been shared with the Russian president.

Driving the news: President Biden on Friday blamed the Kremlin for Navalny's death during remarks at the White House. The president said he had "no doubts" that Putin was responsible.

• Biden said in 2021 that Russia would face "devastating" consequences if Navalny died in prison. He said Friday that his administration was "looking at options" when he was asked about additional sanctions against Moscow over Navalny's death.

Vice President Harris said earlier Friday ahead of a speech at the Munich Security Conference that the U.S. was working to confirm the "terrible news" that Navalny had died.

• "If confirmed, this would be a further sign of Putin's brutality. Whatever story they tell, let us be clear: Russia is responsible," Harris said.
• Navalny's wife Yulia told the conference in Munich that if it was true her husband was dead, "I want Putin, his entourage, Putin's friends and his government to know they will be held responsible for what they have done to our country, my family, and my husband."

Between the lines: Navalny's team had warned repeatedly that he could be killed in prison, and worked to bring international attention to the appalling conditions in which he was being held. They reported that he had been denied medical care in multiple instances, and that other prisoners had been encouraged to torment him.

• On Tuesday, Navalny reported that he had been given "15 days in a punishment cell." He appeared at a court hearing on Thursday and did not appear to be in obvious ill health.

Flashback: Navalny collapsed on a flight from Siberia to Moscow in August 2020. After being transferred to Germany, doctors concluded he had been poisoned with the nerve agent Novichok, a favorite of the Russian security services.

• Navalny defiantly returned to Russia the following January, and was immediately arrested on the Kafkaesque charge of violating parole while recovering from the assassination attempt.
• He was shuttled between prisons for the following three years, occasionally passing messages through his lawyers mocking Putin, opposing the war in Ukraine, or encouraging his family and supporters to continue their work.
• Navalny's team has continued to publish investigations into the wealth and alleged corruption of Putin, his top aides and their families — most famously the "Putin's Palace" video that was viewed more than 100 million times on YouTube.

In his own words: Asked during the Oscar winning 2022 documentary Navalny what his message to the Russian people would be if he were killed, Navalny said:

Editor's note: This story has been updated with additional developments.