The Tunisian army has blocked off a square where rival protesters had confronted each other in Tunis, declaring it a "closed military zone" in an attempt to stem rising unrest.
After protesters clashed Monday in the capital's central Bardo square, where Tunisia's Constituent Assembly is located, the army sealed it off with barbed wire and fencing.
In the flashpoint southern city of Sidi Bouzid, Tunisian police fired tear gas to disperse stone-throwing anti-government protesters after clashes outside municipal offices there.
Tensions have been growing over opposition efforts to oust the Islamist-led government following last week's assassination of a leftist politician, the second such killing in six months.
Protesters say Tunisia's moderate, ruling Ennahda party has not done enough to cut off funding or support for extremists.
The unrest erupted just weeks before the transitional Constituent Assembly was set to complete a draft of a new constitution. The secular opposition now demands that the 217-member body be dissolved. Seventy lawmakers have left it and set up a sit-in outside the assembly offices -- among them, Iyed Dahmani is a member of parliament.
"Will we join the General Assembly on Monday or Tuesday? I answered, and I think that I did in the name of all my colleagues: 'The MPs who retired won't come back to the Assembly neither on Monday, nor Tuesday, nor any other day.' This is our position and we hold it," Dahmani said.
The Ennahda-led government held emergency talks Monday and Tunisia's powerful labor unions were also set to meet to discuss more strike action. On Friday, the unions shut down much of the country for a strike to mourn the leftist politician, Mohamed Brahmi, who was assassinated last week.
Tunisian officials blamed al-Qaida-linked extremist groups for the killing.