Riots took place in the Gafsa region on Thursday, following violence in a nearby region on Wednesday night, when security forces were forced to fire into the air to stop a crowd of protesters attacking a government building.

Tunisia became the birthplace of the "Arab Spring" uprisings when protests forced out the autocratic president in January. In its first democratic election last month, Tunisia voted to hand power to a coalition led by moderate Islamists.

People rioted in two towns in the Gafsa region, 360 km southwest of the Tunisian capital, after they were left off a list of people recruited by a local phosphate mining company.

"There are riots and looting in Om Larayss and Mthila. It started yesterday and continued today," witness Hedi Radaoui told Reuters. "Youths set fire to police stations and buildings of the Gafsa Phosphate Company and the Office of Labour."

A government official said the provincial authorities imposed a curfew in Gafsa, effective from Thursday, from 7 pm (1800 GMT) to 6 a.m., in an effort to prevent further unrest.

"Everything is destroyed here in Mthila .. most shops are closed, roads are blocked, most of the buildings are burned," Amen ben Abdallah, a resident of Mthila, told Reuters by telephone. "The authorities continue to ignore the region and the consequences will be disastrous", he said.

The Gafsa region, near Tunisia's border with Algeria, is the centre of the mining industry. It is also one of the most impoverished areas of Tunisia and has been the scene of several protests and riots since the January revolution.

Late on Wednesday, about 3,000 protesters in the town of Kasserine, about 300 km southwest of Tunis, tried to storm the town prison.

They took to the streets because they felt the authorities had failed to recognise their town's contribution to the revolution earlier this year which forced Zine al-Abidine Ben Ali to flee to Saudi Arabia.

Kasserine was one of the first towns to rise up against Ben Ali's rule. It also suffered some of the highest casualties of the revolution when police opened fire on demonstrators.

Tunisia's revolution delivered democracy to a country which had lived under autocratic rule since its independence from France half a century ago.

But instead of improving living standards, as many people hoped, the revolution made the average Tunisian worse off.

Tourists, the main source of foreign revenue, and some investors were scared off by the instability that accompanied the uprising. Economic growth has slumped and unemployment is forecast to rise this year.

The moderately Islamist Ennahda party, which dominates the governing coalition, has said it is committed to creating jobs, especially for towns away from the more affluent areas on the Mediterranean coast.