Russia on Monday sentenced Kremlin critic Vladimir Kara-Murza to 25 years in jail on charges including treason, amid an intensifying crackdown on opposition voices since Russia launched its Ukraine offensive.

Following a closed-door trial, the court said it found Kara-Murza guilty of high treason, spreading "false" information about the Russian army and being affiliated with an "undesirable organisation", according to an AFP journalist present in the Moscow court.