Russian Opposition Leader Who Was A Healthy 47 Years Old Dies In His Cell

Russia's most significant opposition leader for the past decade, Alexei Navalny, has died in an Arctic Circle jail, the prison service has said.

President Vladimir Putin's most vociferous critic, he was serving 19 years on extremism charges that were widely seen as politically motivated.

Navalny was moved to one of Russia's toughest penal colonies late last year.

His wife Yulia has appealed to the international community "to help punish this regime".

The prison service in Russia's Yamalo-Nenets district where Navalny was being held said he had "felt unwell" after a walk on Friday.

He had "almost immediately lost consciousness", it said in a statement, adding that an emergency medical team had immediately been called and tried to resuscitate him but without success.

"The emergency doctors declared the prisoner dead. Cause of death is being established."

Navalny, 47, was last seen only one day before his death, looking well and laughing during a court hearing via video link.