His spokesman confirmed Alexei Navalny's death, but it remains unclear where the Vladimir Putin critic's body is.
Spokeswoman Kira Yarmysh said in a post on the X website that the most prominent face of Russian opposition to Putin was “killed” in a remote penal colony in the Arctic.
She said Mr Navalny's mother, Lyudmila Navalnaya, was told by authorities that her son died on February 16 at 2.17pm local time.
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Prominent Navalny ally Ivan Zhdanov added that prison officials told Mr. Navalny's mother that he died of “sudden death syndrome.”
But the 47-year-old's body has not yet been located or released by authorities.
Alexei Navalny's mother was unable to see her son's body. Photo: Reuters
Yarmysh said Navalny's mother was told by a prison official that her son's body had been transferred to the nearby city of Salekhard as part of the investigation into his death.
But when they arrived at the morgue, it was closed, and workers said the body was not there.
Hours later, Ms Yarmysh said the politician's lawyers had been informed that Mr Navalny's body would not be handed over to his relatives until the investigation into his death had been completed.
The investigation committee in Salekhard was accused of “running us in circles and covering their tracks” just hours before they were informed that the investigation had already concluded, and nothing criminal had been proven.
Photo: AP
Russia's Federal Prison Service said on Friday that Navalny felt ill after walking and lost consciousness in the punishment colony in the town of Kharp, in the Yamalo-Nenets region, located within the Arctic Circle.
More than 340 detainees in Russia
Meanwhile, more than 340 people have been arrested in Russia since the moment Navalny's death became public, according to the independent human rights organization OVD-Info.
This included 230 people in multiple cities who were arrested on Saturday.
Photo: AP
Photo: Reuters
Others were arrested the day before when they came to lay flowers in memory of Mr. Navalny, OVD-Info said.
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Among those detained was a priest who went to a memorial in St. Petersburg to conduct a mass in memory of the politician.
In Moscow, footage on social media showed a large group of people chanting “shame” as police pulled a screaming woman from the crowd.
Salute to Navalny. Photo: AP
Putin 'must take responsibility'
Hours after Navalny's death was announced, his wife said: Yulia Navalnaya made a dramatic appearance at a security conference in Germany Where many world leaders met.
She said she wasn't sure if she could believe the news from official Russian sources, “but if it's true, I want Putin and everyone around Putin and Putin's friends and his government to know that they will be held accountable for what they did to us.” “My country, my family, and my husband.”
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Starmer: Navalny was incredibly brave
In response, Labor leader Sir Keir Starmer said he was “moved” by Ms Navalnaya's words, adding that Russia must be held to account.
This came after the United Kingdom Foreign Minister Lord Cameron “We must hold Putin accountable for this,” he said. “No one should doubt the horrific nature of Putin’s regime in Russia after what just happened.”
The foreign ministers of the Group of Seven, made up of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States, called on Russia to fully explain the circumstances of Navalny's death.
