Alexei Navalny's death listed as 'natural,' mother says, accusing Russia of blackmail

Alexei Navalny's cause of death has been listed as "natural" on his medical report, according to Navalny's spokesperson Kira Yarmysh, who was relayed the information on the death certificate by the Russian opposition leader's mother.

"The medical report on death shown to the mother of Alexei Navalny stated that the causes of death were natural," Yarmysh wrote in Russian on X, the social media platform formerly known as Twitter.

Navalny's team has accused Russia of killing the Vladimir Putin critic, who was previously poisoned and nearly died in an assassination attempt blamed on the Russian president.

Alexei Navalny's mother, Lyudmila Navalnaya, said she was "secretly" taken to the morgue to see her son's body in a video message posted to YouTube on Thursday. She also said the Russian government is blackmailing her and trying to force her to have a secret funeral for her son.

"I just left the building of the Investigative Committee of the city of Salekhard. I spent almost a day there alone, alone with investigators and criminologists. They only let the lawyer in this afternoon. Yesterday evening they secretly took me to the morgue, where they showed Alexei," Navalnaya said in the video.

Navalny's body was taken to the Russian city of Salekhard, located on the Arctic Circle, after he died in a nearby penal colony on Feb. 16.

Investigators "claim they know the cause of death," Navalnaya said. She also said she signed Navalny's death certificate.

"They have all the medical and legal documents ready, which I saw, and I signed the medical death certificate," Navalnaya said.

Navalnaya said the Russian government is "blackmailing" her, trying to convince her to have a secret funeral for her son.

"I'm recording this video because they started threatening me. Looking into my eyes they say that if I don't agree to a secret funeral, they will do something with my son's body," Navalnaya said. "I don't want any special conditions. I just want everything to be done according to the law. I demand that his son be given to me immediately."

White House spokesperson John Kirby hammered Russia on the reporting that they were making demands of Navalny's mother in order for her to receive his body.

Kirby said he could not confirm that she was being "blackmailed," but, "nevertheless, this is the man's mother."

"It's not enough that she gets to see the body of her son," Kirby said. "She should be able to collect the body of her son so that she can properly memorialize her son and her son's bravery and courage and service and do all the things that any mother would want to do for a son lost in such a tragic way. The Russians need to give her back her son and they need to answer for what specifically befell Mr. Navalny and acknowledge that they, in fact, are responsible for his demise."

President Joe Biden addressed the U.S. following news of Navalny's death last week, saying he was both "not surprised and outraged" while placing the blame directly on Putin.

"We don't know exactly what happened but there is no doubt that the death of Navalny was the result of something that Putin and his friends did," Biden said.

Biden met with Navalny's wife and daughter in San Francisco Thursday, according to a readout from the White House and photos the president posted to X.

"Today, I met with Yulia and Dasha Navalnaya – Aleksey Navalny's loved ones – to express my condolences for their devastating loss," Biden wrote on X. "Aleksey's legacy of courage will live on in Yulia and Dasha, and the countless people across Russia fighting for democracy and human rights."

ABC News' Rashid Haddou, Molly Nagle and Justin Gomez contributed to this report.