Tunisian authorities said Friday the number of people detained in a wave of violent protests had risen to nearly 800, as fresh unrest over austerity measures hit a provincial town overnight.

Activists have called for a major protest Friday in the capital Tunis over the measures introduced at the start of the year that are expected to see prices rise.

An AFP correspondent in the northern town of Siliana reported that police fired tear gas at dozens of youths who pelted them with stones for some three hours overnight.

But the situation appeared calm in other flashpoint towns and neighbourhoods across the country that had seen clashes that left dozens of police officers injured.

Interior ministry spokesman Khalifa Chibani said 151 people were arrested Thursday, taking the number detained for alleged involvement in the violence to 778 after several nights of unrest.

Chibani told local radio that clashes between youths and police were "limited" and "not serious", and insisted no acts of violence, theft or looting were recorded Thursday evening.

Amnesty International on Friday accused the Tunisian authorities of using "increasingly heavy-handed methods to disperse rallies and subsequently arrest protesters" during the unrest.

"Tunisian security forces must refrain from using excessive force and end their use of intimidation tactics against peaceful demonstrators," the rights group said.

One man died in the unrest on Monday night, but the authorities have insisted the police were not responsible.

A number of left-wing activists have been arrested by the authorities in recent days, after officials accused them of fuelling the violence.

Several dozen members of the Popular Front party demonstrated Friday in front of a court in the town of Gafsa after the arrest of several local activists, an AFP correspondent said.

Tunisia is considered a rare success story of the Arab Spring uprisings that began in the North African country in 2011 and spread across the region, toppling autocrats.

But the authorities have failed to resolve the issues of poverty and unemployment.

Protests are common in Tunisia in January, when people mark the anniversary of the revolution that ousted long-time dictator Zine El Abidine Ben Ali.