Injured Ukrainian activist Dmytro Bulatov has been flown to Lithuania for medical treatment.
The 35-year-old, who claims to have been abducted and tortured for over a week by mysterious kidnappers, was allowed to leave hospital after Western diplomatic intervention.
The Ukrainian police had wanted to arrest him.
Bulatov was a leader of a group called Automaidan, made up of drivers who have been protecting the protest camps.
Fear of more attacks against activists has prompted opposition action:
“We need to organise self-defence units to control law and order on the streets in every city and every town. Call your friends, call your neighbours, patrol the streets. Only we ourselves can stop this lawlessness organised by the authorities with the help of moronic thugs,” opposition leader Vitaly Klitschko told protesters in Maiden Square.
President Viktor Yanukovych who last week made a few concessions to protesters, including repealing some anti-protest laws, returns to work on Monday after being ill.