By Tarek Amara
TUNIS (Reuters) - Tunisian police fired into the air to disperse rioters in the capital early on Sunday, and were attacked by crowds throwing petrol bombs in another city, in the most violent clashes yet involving Islamists.
The rioting is the starkest sign to date of the friction between Tunisia's secular establishment and Islamists who have been growing more assertive since the country's autocratic leader was ousted in a revolution six months ago.
Sunday's violence was sparked by an incident on Friday when police, trying to break up an anti-government demonstration in the center of Tunis, fired tear gas inside a mosque.
In the Intilaka district in the west of Tunis, about 200 youths -- many of them with the beards typical of Islamists -- set fire to a police station.
Police responded by shooting into the air and using tear gas, while a police helicopter hovered over the district, according to a Reuters reporter who witnessed the clashes. The clashes continued until about 3:00 a.m. local time.
People in the crowd chanted "Allahu Akbar!" or "God is greatest!" They also shouted "You attacked Islam!" and "We are not afraid of your police!"
In the town of Menzel Bourguiba, about 70 km (45 miles) north of Tunis, four police officers were wounded in clashes with rioters, a police source told Reuters.
"Angry youths threw stones and Molotov cocktails at the police before heading to a police station to set it on fire," said the police source, who spoke on condition of anonymity.
"It was a terrible night ... We don't know what caused it but it is clear that among them (the rioters) there were lots of people with beards," said the source.
Tunisians overthrew autocratic leader Zine al-Abidine Ben Ali in a revolution in January that electrified the Arab world and inspired uprisings in Egypt and elsewhere.
Since then the caretaker authorities, who say they are committed to dismantling Ben Ali's repressive rule, have lifted a ban on Islamist parties and released hundreds of their followers from prison.
But the Islamists' resurgence has led to friction with the country's establishment and some people, who believe the Islamists are becoming too powerful and could undermine the country's secular values.
Anti-government activists not linked to the Islamists called for further demonstrations for later on Sunday in Tunis, and the provincial cities of Gafsa and Gassrine.
The secular opposition activists say the caretaker government has not made a clear break with Ben Ali's rule and that it is back-tracking on commitments to build a democratic system.
"This is our opportunity to renew the revolution," wrote one person on a Facebook page used by opposition activists. "It is time for the revolution to succeed."
(Writing by Christian Lowe; Editing by Elizabeth Piper)