The clashes between police and Saakashvili adversaries were the first major unrest since anti-government demonstrations began in early April in Tbilisi.
They come a day after the authorities said they had thwarted an army mutiny at a base outside the capital.
Later in the evening, opposition leaders and supporters gathered outside parliament for a rally, as they have daily since 9 April.
Attendances at the rallies have dwindled but tensions in the city appear to be rising.
The protesters are calling for the resignation of President Mikhail Saakashvili over his leadership record and his handling of Georgia’s war with Russia last summer.
Police accused protesters of trying to storm their base, and television pictures showed police and demonstrators trading blows with batons and sticks across a metal gate dividing them.
Several hundred people converged on the building, where riot police took position in the grounds. The Interior Ministry said 22 protesters and six policemen were wounded. The opposition said several of its leaders were also treated in hospital.
Riot police used batons on protesters trying to enter a police compound where three people were being held over the alleged beating of a local journalist.
The drama cast a shadow over the launch of NATO military exercises in Georgia on Wednesday, condemned by Russia as “muscle-flexing” on its southern border.
Georgia has been braced for unrest since the opposition began daily protests on April 9, blocking streets in downtown Tbilisi and demanding Saakashvili quit over his record on democracy and last year’s war, when Russia crushed a Georgian assault on breakaway South Ossetia, BBC reports.
