Moscow, Feb. 16: Jailed Russian upposition leader Alexei Navalny has been declared dead by the prison service of the Yamalo-Nenets region, where he had been serving his sentence.

In a statement published on its website, the Federal Penitentiary Service of the Yamalo-Nenets Autonomous District said that Navalny “felt unwell” after a walk on Friday, and “almost immediately lost consciousness”, Reuters reported.

Stating that medical staff had been called, but that they were unable to resuscitate Navalny, it said the reason of death was being established.

Meanwhile, Kremlin has claimed that it has no information on the cause of Navalny’s death, and added that the prison service was making all the checks regarding his death.

Russia’s Investigative Committee has launched a procedural probe into the death, the Investigative Committee said.

Russian newspaper editor and Nobel Peace Prize laureate Dmitry Muratov told Reuters that the death of jailed opposition leader Alexei Navalny was “murder”, and said that he believed prison conditions had led to his demise.

Alexei Navalny, Russia’s most prominent opposition leader and a vociferous Putin critic, was sentenced to 19 more years in prison by a Russian court in August last year on an extremism conviction. Navalny has been behind bars in Russia since January 2021, when he returned to Moscow after recuperating in Germany from nerve agent poisoning that he blamed on the Kremlin. Before his arrest, he campaigned against official corruption and organized major anti-Kremlin protests.

He has since received three prison terms and spent months in isolation in Penal Colony No. 6 for alleged minor infractions. He has rejected all charges against him as politically motivated.

The prison colony, where Navalny was serving his sentence, is infamous for severe conditions in the Yamalo-Nenets region, about 1,900 km (1,200 miles) northeast of Moscow.-Agencies