Russian authorities have brought treason charges against a prominent opposition activist who was jailed for allegedly spreading “false information” about Russia’s military operation in Ukraine.

The charges against Vladimir Kara-Murza Jr stem from speeches he gave in several western countries that criticised the Kremlin’s rule, according to the activist’s lawyer, Vadim Prokhorov.

“These speeches did not carry any threat to the country; it was public, open criticism,” Mr Prokhorov told Russian state news agency Tass.

Mr Kara-Murza denies committing treason, the lawyer said. If convicted, he faces a possible prison sentence of up to 20 years.

Mr Kara-Murza was jailed in April on a charge of spreading “false information” about the Russian military. The charge followed a March 15 speech he gave to the Arizona House of Representatives in which he denounced Russia’s military action in Ukraine.

Russia adopted a law criminalising spreading “false information” about its military shortly after Russian troops rolled into Ukraine on February 24.

Authorities have used the law, which authorises a prison sentence of up to 15 years for a conviction, against dozens of people to stifle opposition to what the Kremlin calls “a special military operation.”

Mr Kara-Murza, a journalist, was an associate of opposition leader Boris Nemtsov, who was killed near the Kremlin in 2015. He himself survived poisonings in 2015 and 2017 that he blamed on the Kremlin. Russian officials have denied responsibility.