Tunisian President Zine al-Abidine Ben Ali fired his interior minister on Wednesday to try to staunch the worst unrest in decades, but fresh clashes with police broke out and witnesses said one man was killed.

The government has declared a nightly curfew starting on Wednesday for the capital and surrounding suburbs, an official told Reuters.

Despite the deployment of the military in many areas and a heavy police presence, stone-throwing youths confronted police in a suburb of the capital and witnesses said there were renewed protests in two provincial towns.

People taking part in the unrest say they are angry about unemployment, corruption and what they say is government repression. Officials say the protests have been hijacked by a minority of violent extremists who want to undermine Tunisia.

The unrest is the worst Ben Ali has faced in his more than two decades in office rule. Officials said earlier this week that 23 civilians have been killed since the clashes first broke in December.

The curfew, which will continue for an indefinite period, will begin at 8:00 p.m. (7:00 p.m. British time) each night and end at 6:00 a.m. in the morning, said the official in the state's communications agency.

Two witnesses told Reuters that police in the town of Thala, 200 km southwest of Tunis, used teargas to try to disperse a crowd of people but when that had no effect they opened fire, killing 23-year-old Wajdi Sayhi.

Officials could not immediately be reached to confirm the account. The victim was deaf, said his brother, Ramzi.

The police told him to go home but he heard nothing, and they fired towards him, he told Reuters by telephone. They (the government) promised us and promised us and now they have promised us death, he said.

Some analysts say the Tunisian government is likely to be able to contain the unrest but that in the longer term Ben Ali could find himself weakened and his opponents emboldened.

Adding to mounting international pressure on Tunisia over its handling of the protests, the European Union, Tunisia's biggest trading partner, said the violence was unacceptable.

We cannot accept the disproportionate use of force by the police against peaceful demonstrators, Maja Kocijancic, spokeswoman for EU foreign affairs chief Catherine Ashton, told a regular briefing.

Military Humvee jeeps and armed soldiers were patrolling at least two locations in the centre of Tunis on Wednesday and most shops were shut. Witnesses said thousands of people gathered in the provincial town of Gassrine chanting Ben Ali, go away!.

CONCESSIONS

Some international human rights groups say the death count is higher than officials admit. The government dismissed. It says the deaths came about when police fired in self-defence on rioters armed with petrol bombs and sticks.

Prime Minister Mohamed Ghannounchi, speaking at a news conference, said that the president had decided to appoint Ahmed Friaa, an academic and former junior minister viewed as a technocrat, as the new interior minister.

He did not give a reason for the change but he said the president has announced the creation of a committee of investigation into corruption and to assess the mistakes of certain officials.

In further concessions, he said Ben Ali had decided to free everybody detained over for taking part in the riots and promised financial help to jobless graduates -- a group whose grievances have been a driving force behind the unrest.

The protests, now entering their fourth week, are being watched closely in other countries in the Arab world with the potential for social unrest.

A Reuters reporter in the Ettadamen district of Tunis, where police fired warning shots to disperse protesters on Tuesday night, said a crowd of several hundred youths was throwing stones at police and they were responding by firing tear gas.

The unrest has alarmed investors in Tunisia, one of the region's most developed economies. Shares on the Tunis stock exchange closed 3.4 percent down on Wednesday to reach their lowest level in 38 weeks.

European union Unemployment Human rights Tunisia