TUNIS, JULY 16 -- Rioting broke out in central Tunis today as a confrontation between Islamic militants and the government of President Habib Bourguiba reached its most violent pitch yet.

Several hundred protesters gathered in the city center around lunchtime, chanting slogans and waving banners bearing the name of Tunisia's leading religious organization, the Islamic Tendency Movement.

They marched through the streets, sending office workers and tourists scattering for cover, before being confronted by police units. Street battles developed, with the heavily outnumbered police coming under a hail of rocks and gasoline bombs. Tires were burned and several vehicles attacked.

Clouds of tear gas hung over the city center when police reinforcements, some in armored troop carriers, dispersed the protesters. There was no word of casualities or arrests.

The Islamic Tendency Movement has staged less violent demonstrations in Tunis and other cities in recent months to protest a crackdown by the authorities.

Since the end of March, when the government announced that it had evidence of a fundamentalist coup plot, about 2,000 people are believed to have been detained.

Despite the severity of the tactics, disturbances have continued. Fundamentalist leader Rachid Ghannouchi has been detained but other leading members of his organization remain at large.

Many Tunisians have remained skeptical that the extremists, who are said to have received support from Iran, pose a genuine threat to the established order. The movement has denied plotting.