Police in Tunisia have fired warning shots and tear gas to disperse crowds of protesters in the centre of the capital, Tunis.
Witnesses say several people were injured.
Tens of thousands filled the streets of the capital earlier in the day, calling for the resignation of Prime Minister Mohammed Ghannouchi, an ally of the ousted president Zine al-Abedine Ben Ali.
Anger and disillusionment with the interim government is commonplace in Tunisia, whose revolt sparked protests across the Arab world.
“What are the courts doing?” asked one man, visibly angry, “Where is the justice for the 170-plus martyrs who died during January’s revolution? We want their killers to be put on trial.”
The interim government is meant to be organising elections in Tunisia, but has undergone several changes.
Ghannouchi was prime minister for ten years under Ben Ali’s rule, which Tunisians saw as oppressive and corrupt.