In Thala, near the Algerian border, troops were sent in after protesters burned down the national security building, forcing police to retreat from the town, witnesses said.
The immediate cause of the unrest is government-imposed price and tax rises, which will raise the cost of basic goods but are said to be essential to cut a ballooning deficit and satisfy international lenders.
Longer-term factors include high levels of poverty and youth unemployment, particularly among graduates.
While Tunisia is widely seen as the only democratic success story among Arab spring states, it has had nine governments since the overthrow of the authoritarian leader Zine al-Abidine Ben Ali, none of which have resolved the growing economic problems.
“Some 330 people involved in acts of sabotage and robbery were arrested last night,” said the interior ministry spokesman, Khelifa Chibani, bringing the number of detainees since the protests began to about 600.
The army was also deployed in several other cities, including Sousse, Kebeli and Bizert to protect government buildings that have become a target for protesters.
Protests have become common in Tunisia in January, the anniversary of the 2011 revolt, which was sparked by the death of Mohamed Bouazizi, a street seller who set himself on fire in a protest over unemployment and police harassment.
This year’s protests have drawn in hundreds in each town where they have taken place, though they have been smaller than previous waves of demonstrations since 2011.
On Wednesday, the prime minister, Youssef Chahed, accused the opposition of fuelling dissent by calling for more protests.
Chahed, who heads a coalition of secular and Islamist parties, has said that 2018 will be a difficult year for Tunisia but the economy will improve rapidly once the new measures take effect.
International lenders extended a crucial $2.8bn (£2.1bn) loan to Tunisia in 2015, but have demanded cuts to the civil service and a broader austerity programme.
Overseas analysts will be watching closely. Europe is concerned about stability in Tunisia partly because unemployment there has forced many young Tunisians to go abroad. The number of boats smuggling migrants to Italy has been rising and Tunisia has also produced significant numbers of recruits for Islamic State.
Among the hundreds arrested on Tuesday were two radical Islamists who had helped storm a police station in Nefza town, the interior ministry spokesman said. In Tunis, a crowd stormed a Carrefour market.
On Tuesday, petrol bombs were thrown at a Jewish school on the southern tourist island of Djerba, home to an ancient Jewish community.
Tunisia suffered two militant attacks in 2015 which damaged foreign investment and tourism, which accounts for 8% of Tunisia’s economic activity.
Source: The Guardian