Georgia's opposition parties have called on President Mikhail Saakashvili to resign as thousands of protesters continued to rally for the second day in the capital, Tbilisi.

Opposition leaders announced the decision Saturday at a mass rally attended by some 12,000 protesters who chanted "Go, go!" Activists are calling for early parliamentary elections next spring, changes in election laws and restrictions on presidential powers.

They also demand a release of political prisoners.

The crowd was smaller than the estimated 50,000 protesters who rallied in front of the parliament building on Friday.

President Saakashvili has not made any public comment regarding the rally, but parliamentary Speaker Nino Burdzhanadze met with the opposition representatives on Friday.

President Saakashvili is facing his worst political crisis since coming to power as a hero in 2003, following massive protests known as the Rose Revolution.

The opposition has accused the pro-western president of becoming increasingly authoritarian and of abusing power to eliminate political rivals. Activists say they will not give up until their demands are met.

They also demand the release of several prisoners, including Irakli Batiashvili, a leading member of the opposition Forward Georgia Party. He was sentenced in May to seven years in prison on charges of supporting rebels in Georgia's breakaway Abkhazia region.

Batiashvili's arrest and sentencing sparked a wave of protests earlier this year.

Some information for this report was provided by AFP and AP.