The activist, Dmytro Bulatov, said unidentified captors who held him for more than a week had cut off an ear and driven nails through his hands before dumping him in a forest.
Ukraine's interior ministry was later reported by Interfax as saying Bulatov would be placed under house arrest for a week under suspicion of organising major unrest.
His fate, as well as Ukraine's wider political crisis, stirred much debate at the Munich Security Conference, a three-day meeting of political, diplomatic and military leaders.
German Foreign Minister Frank-Walter Steinmeier told journalists he had addressed Bulatov's case in talks with his Ukrainian counterpart Leonid Kozhara.
"The foreign minister has said that he (Bulatov) may leave the country if he wants to," said Steinmeier, without giving an indication that this was indeed Bulatov's intention.
Steinmeier labelled the concession from the Ukrainian government "a small success" and reiterated an offer to Bulatov to seek medical treatment in Germany.