Jailed Russian opposition figure and outspoken Kremlin critic Alexey Navalny, who made global headlines when he was poisoned with a nerve agent in 2020, has died, the Russian prison service said.

Navalny had long been a thorn in the side of President Vladimir Putin, exposing corruption in high places, campaigning against the ruling United Russia party, and orchestrating some of the biggest anti-government protests seen in recent years.

He returned to Russia in 2021 and was swiftly arrested on charges he dismissed as politically motivated. He has been incarcerated ever since.

Navalny was sentenced to 19 years in prison in August, after he was found guilty of creating an extremist community, financing extremist activists and various other crimes. He was already serving sentences of 11-and-a-half years in a maximum security facility on fraud and other charges he denies.

Supporters of Navalny claimed his arrest and incarceration were a politically motivated attempt to stifle his criticism of Putin.