Tunisian President Moncef Marzouki and the head of the National Assembly have signed the country's new constitution, officially adopting a charter that is one of the country's last steps to full democracy after a 2011 uprising.
Tens of thousands of Tunisians crowded the streets of Tunis to demand the government's ouster, in the largest opposition protests to hit the capital since the country's political crisis began two weeks ago.
The secular opposition is trying to topple the Islamist-led government and dissolve a transitional Constituent Assembly that is only weeks away from finishing a draft constitution and new election law.
The protest marks the six-month anniversary of the assassination of leftist politician Chokri Belaid, one of two opposition figures to be shot dead in recent months.
Tunisian police fired teargas to disperse violent protests in the southern town of Sidi Bouzid, cradle of the country's revolution and hometown of slain opposition figure Mohamed Brahmi, witnesses told Reuters.
Angry demonstrators, who came out to protest Thursday's assassination of Brahmi, threw rocks at police, said local resident Mahdi al-Horshani.
"Hundreds of protesters lit tyres on fire to block roads and they threw rocks at the police," he said. "There is a lot of anger and frustration at the situation."
A bomb in a police car exploded this morning in the Tunisian capital of Tunis hours before the funeral of assassinated secular opposition politician Mohamed Brahmi, a spokesman at the Interior Ministry said.
There were no casualties from the blast near a police station in the residential La Goulette district, Mohammad Ali Aroui said.