The youth organization of the opposition United National Movement (UNM) party rallied in front of the EU Delegation to Georgia office on Monday.
Demonstrators dressed as prisoners demanded the release of UNM Chair Nika Melia and co-founder of the TV channel Mtavari Arkhi Giorgi Rurua.
Rally participants said they wanted to pass on their demand to the EU mediator Christian Danielsson.
EU mediator Danielsson returned to Tbilisi on Sunday to help the opposition and the government reaching an agreement. Danielsson is holding meetings with the ruling team and the opposition.
Danielsson first arrived in Tbilisi on March 12. He decided to prolong his stay in Tbilisi to help the sides. After a five-day mediation that ended with no result, he left the country.