On Friday night the capital remained under a tight curfew. Groups of more than two people were forbidden on the streets after 5 p.m., and no one was allowed out after 8 p.m. State news media warned that the police would shoot curfew violators on sight. Tanks and other security forces were deployed around the city, and the airport was shut down.

As night fell, gangs of security forces armed with machine guns and clubs could be seen chasing down stragglers. Dozens have died in clashes with the police over the last week, and continued gunshots were reported well after curfew on Friday night from several neighborhoods around the capital as sporadic riots continued.

Image Credit... The New York Times

The United States had counted Tunisia under Mr. Ben Ali as an important ally in battling terrorism. But on Friday, President Obama said in a statement that he applauded “the courage and dignity of the Tunisian people.”

“The United States stands with the entire international community in bearing witness to this brave and determined struggle for the universal rights,” he said, adding, “We will long remember the images of the Tunisian people seeking to make their voices heard.”

The antigovernment protests began a month ago when a college-educated street vendor named Mohamed Bouazizi in the small town of Sidi Bouzid burned himself to death in despair at the frustration and joblessness confronting many educated young people here. But the protests he inspired quickly evolved from bread-and-butter issues to demands for an assault on the perceived corruption and self-enrichment of the ruling family.