affected by the tear gas were taken to hospital, an official there said, adding that none of them was seriously hurt.

The demonstrators had been chanting anti-government slogans such as "The people want the regime to fall!" accusing the ruling elite of "hypocrisy" and demanding the right to work.

Several opposition groups took part in the protest, including the Republican Party, the Tunisian Workers Party and Al-Watan, as well as political independents.

"The people's demands for an improvement in their quality of life are becoming more and more insistent, but unfortunately the government is not there to serve the people," Mohammed Ghadri, a member of the Republican Party, told AFP.

A similar incident took place at the end of June, when protesters angered over their living conditions attacked the same building, hurlingrocks and burning tyres, with police firing tear gas to disperse them.

The Tunisian Workers Party denounced the forceful tactics used by the police on Thursday and reiterated its support for the protesters' demands, including the dismissal of the provincial governor, the head of the national guard and the public prosecutor.

It also called for the freeing of four protesters it said were arrested.

Sidi Bouzid is where the uprising began that eventually toppled former dictator Zine El Abidine Ben Ali and touched off the Arab Spring, when a street vendor immolated himself in December 2010 in protest over his own precarious livelihood.

The town is located in a particularly marginalised region, and little has improved since the revolution, according to analysts.

"The residents of Sidi Bouzid live in very difficult conditions, especially