Vladimir Kara-Murza: Putin opponent in isolation cell in Siberian jail

Mr Kara-Murza was jailed for 25 years on charges of treason and lying about the war Ukraine

Jailed Russian opposition activist Vladimir Kara-Murza has been moved to a maximum-security prison in Siberia, several weeks after he was taken from a Moscow detention centre.

He was placed in an isolation cell at the Omsk penal colony, his lawyer says.

Mr Kara-Murza, who has survived two poisonings since 2015, was jailed for 25 years in April accused of treason and lying about the war Ukraine.

His lawyer said conditions in Omsk threatened his client's health.

The whereabouts of the 42-year-old had been unknown for several weeks.

The charges against him stemmed from a speech he gave to the Arizona House of Representatives, in which he denounced Russia's invasion of Ukraine.

His sentence is the longest against a Russian opposition figure in recent years.

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His lawyer, Vadim Prokhorov, said in a Facebook post that Mr Kara-Murza arrived last week at IK-6, a maximum security penal colony.

"He was straight away placed in an isolation cell," he added.

He warned that such treatment would be detrimental for his client's health, which has already been weakened due to poisoning attempts his client has blamed on the Kremlin.

Mr Kara-Murza's lawyers and family have said the attempts on his life have left him with a nerve condition called polyneuropathy.

He has long campaigned for Western countries to place sanctions on Russian officials. He has rejected the charges against him and called them punishment for standing up to President Vladimir Putin.

Omsk is some 2,700km (1,670 miles) east of Moscow. Russia's penal system often takes weeks to move prisoners by rail between jails, with the whereabouts of those transit often unknown.