Police used teargas to disperse protesters taking part in another anti-government demonstration in Tunis Sunday amid mounting violence in the country as youths torched police stations in five cities.

About 200 protesters gathered outside the municipal theatre and along the Habib Bourguiba Avenue in central Tunis and sang the national anthem to galvanise support.

They hurled insults at police who responded by warning the demonstrators to clear the streets and return home.

When the protesters refused and taunted police by calling them "cowards", security forces fired teargas, forcing the demonstrators to move into nearby streets before they reappeared in small groups on the main avenue.

On Saturday, authorities imposed a night time curfew in Tunis and its outskirts after several days of violence.

The capital has been rocked by a series of protests against the transitional government, installed following the January uprising that led to the fall of president Zine El Abidine Ben Ali after 23 years in power.

Young men armed with knives, chains, sabres and gas bombs burned down five police stations in five cities including Mnihla, Intilaka, Ibn Khaldoun, El-Mourouj V and Kasserine, an interior ministry official told AFP.

Militia loyal to the now defunct party of Ben Ali "are paying young people to sow trouble in the country", the official said, declining to give details.

Youths had ransacked and pillaged a major electrical goods store and a pharmacy and set fire to several vehicles the previous day in Ettadhamen, a deprived district outside Tunis.

Tunisian authorities on Sunday urged people to respect the curfew, warning that all offenders would be prosecuted.

The interior and defence ministries in a statement carried by state media TAP called on the population to "show civic duty and strong responsibility in order to help calm the situation and for its return to normal".

It is unknown how long the curfew, which runs from 9:00 pm to 5:00 am (2200 GMT to 0600 GMT), will remain in place.