Jailed Russian opposition leader Alexei Navalny is dead, the Federal Prison Service says.

The service said in a statement Navalny felt unwell after a walk on Friday and lost consciousness.

An ambulance arrived to try to rehabilitate him, but he died.

Navalny was moved in December from his former prison in the Vladimir region of central Russia to a “special regime” penal colony – the highest security level of prisons in Russia – above the Arctic Circle.

His allies decried the transfer to a colony in the town of Kharp, in the Yamalo-Nenets region about 1900km northeast of Moscow, as yet another attempt to force Navalny into silence.

The remote region is notorious for long and severe winters. Kharp is about 100km from Vorkuta, whose coal mines were part of the Soviet gulag prison-camp system.

The Kremlin said President Vladimir Putin had been informed of Navalny’s death, state media reported.

Navalny, 47, earned admiration from Russia’s disparate opposition for voluntarily returning to Russia in 2021 from Germany, where he had been treated for what European laboratory tests indicated was an attempt to poison him with a nerve agent.

Navalny claimed he was poisoned in Siberia in August 2020.

The Kremlin denied trying to kill him and said there was no evidence he was poisoned with a nerve agent.

–AAP