Police in a Tunisian town used tear gas Thursday to break up a crowd of about 200 hardline Islamists, armed with sticks, swords and petrol bombs, who set fire to a police station, witnesses told Reuters.

The security forces are chasing about 200 Salafists armed with swords and sticks after an exchange of petrol bombs and tear gas, resident Omar Inoubli told Reuters by telephone from Jandouba, about 160 km (99 miles) west of the capital.

These groups set fire to a police station .... (They) are broadcasting recordings through the loudspeakers of mosques calling for jihad (holy war).

Residents said the clashes broke out when police arrested a Salafist but tensions had been brewing between authorities and the conservative Islamists who have become more active since last year's revolution.

The situation has become serious in the city, which has been living in a state of terror and fear because of Salafist groups seeking to impose a strict way of life, another witness, a woman who did not want to be named, told Reuters.

One resident said the Salafis had threatened people drinking alcohol and slapped women wearing trousers or skirts.

NEW FREEDOMS

Tunisia became the birthplace of the Arab Spring uprisings just over a year ago when a wave of protests forced long-standing secularist leader Zine al-Abidine Ben Ali to flee the country.

After the revolution, measures outlawing Islamists were abolished, and a moderate Islamist movement, Ennahda, was elected to lead a coalition government.

The Salafists, who represent a small minority of Tunisians, have profited from the new freedoms. They have attacked brothels, bars and cinemas showing films they consider to be morally suspect, and staged protests to demand an end to mixed-gender classes at universities.

While many renounce violence, some have been linked to al Qaeda's north African branch.

The Salafists represent an awkward problem for Tunisia's Islamist-led government.

Ennahda does not share their hardline views but if it cracks down on them, it risks alienating some of its more conservative supporters. As a result, it has been accused by secularist opponents of being too soft on the group.

(Reporting By Tarek Amara; Editing by Sophie Hares)