Tunisian protesters burned down a regional national security headquarters near the Algerian border, prompting authorities to send in troops after police retreated.
The protests come as unrest over prices and taxes rages across the country, with the government refusing to revise austerity measures in the 2018 budget.
Around 600 people have been arrested, including more than 300 overnight.
Army troops have been deployed in several cities to help quell the unrest.
It comes seven years after the overthrow of autocrat Zine El-Abidine Ben Ali in the first of the Arab Spring revolts.
In Thala, near the Algerian border, soldiers were sent in yesterday evening after crowds set fire to the region’s national security building, forcing police to retreat from the town.
Tunisia’s unity government, which includes Islamists, secular parties and independents, has portrayed the unrest as driven by criminal elements.
“The government will not revise the budget or even some of its articles because some troublemakers have come out in the street,” Investment Minister Zied Ladhari told Mosaique FM radio.
Prime Minister Youssef Chahed has accused the opposition of inciting unrest.
Rejecting the charge, the main opposition group, the Popular Front, called for a major protest in Tunis on Sunday to coincide with the seventh anniversary of Ben Ali’s fall.
Anti-government protests have flared in a number of cities and towns since Monday against price and tax increases.
The army has been deployed in Kebeli, Bizerte and the seaside resort city of Sousse among other towns to protect government buildings that have been targeted by protesters.