A Tunisian soldier screams as he tries to calm down rioters during clashes with the police in downtown of the capital Tunis January 14, 2011. [Photo/Agencies]

The state of emergency remained in effect after the prime minister's announcement, and the streets of central Tunis fell quiet after a day of rioting and volleys of tear gas. A black armored vehicle stood behind the Interior Ministry.

The 74-year-old leader came to power in a bloodless coup in 1987. He took over from a man called formally President-for-Life, Habib Bourguiba, the founder of modern-day Tunisia who set the Muslim country on a pro-Western course after independence from France in 1956.

Ben Ali removed Bourguiba from office for "incompetence," saying he had become too old, senile and sick to rule. Ben Ali promised then that his leadership would "open the horizons to a truly democratic and evolved political life."

But after a brief period of reforms early on, Tunisia's political evolution stopped.

US diplomatic cables released by WikiLeaks have called Tunisia a "police state" and described the corruption there, saying Ben Ali had lost touch with his people. Social networks like Facebook helped spread the comments to the delight of ordinary Tunisians, who have complained about the same issues for years.

Under Ben Ali, most opposition parties were illegal. Amnesty International said authorities infiltrated human rights groups and harassed dissenters. Reporters Without Borders described Ben Ali as a "press predator" who controlled the media.

He consistently won elections with overwhelmingly questionable scores: In 2009, he was re-elected for a fifth five-year term with 89 percent of the vote. Beforehand, he had warned opponents they would face legal retaliation if they questioned the vote's fairness.

The riots started after an educated but jobless 26-year-old committed suicide in mid-December when police confiscated the fruits and vegetables he was selling without a permit. His desperate act hit a nerve, sparked copycat suicides and focused generalized anger against the regime into a widespread, outright revolt.

In Washington, National Security Council spokesman Mike Hammer said the US government, an ally of Tunisia in the war against terror, was monitoring the developments.

"We condemn the ongoing violence against civilians in Tunisia, and call on the Tunisian authorities to fulfill the important commitments made by President Ben Ali in his speech yesterday to the Tunisian people, including respect for basic human rights and a process of much-needed political reform," he said.

Rioters throw stones during clashes with riot police in Tunis January 14, 2011. [Photo/Agencies]