But their new and conspicuous riches, partly exposed in a detailed cable by the American ambassador and made public by WikiLeaks, have fueled an extraordinary extended uprising by Tunisians who blame corruption among the elite for the joblessness afflicting their country.

And on Thursday, idyllic Hammamet became the latest casualty of that rage, as hundreds of protesters swarmed the streets, the police fled and rioters gleefully ransacked the mansion of a presidential relative, liberating a horse from its stable and setting aflame a pair of all-terrain vehicles.

That outburst was just a chapter in the deadly violence that flared around the country and in Tunis, the capital, again on Thursday, making the government appear increasingly shaky. The mounting protests threaten not only to overturn a close United States ally in the fight against terrorism but also to pull back the veneer of tranquil stability that draws legions of Western tourists to Tunisia’s coastal resorts.

President Ben Ali gave a hastily scheduled televised address on Thursday night, his second in the past week, and this time he appeared rattled. He no longer blamed foreign terrorists or vowed to crack down on protesters. Instead, he pledged to give in to many of the protesters’ demands, including an end to the government’s notoriously tight censorship, but rejecting calls for an immediate end to his 23-year rule.

“I am telling you I understand you, yes, I understand you,” Mr. Ben Ali, 74, declared. “And I decided: total freedom for the media with all its channels and no shutting down Internet sites and rejecting any form of monitoring of it.”

And he repeated a pledge he first made when he seized power in a bloodless coup: “No presidency for life.” He vowed not to challenge the constitutional age limit of 75 for presidents, which would make him ineligible to seek re-election in 2014.

The immediate response to the speech appeared mixed. In at least one neighborhood of the capital, grateful Tunisians could be heard in the streets, ignoring an 8 p.m. curfew order, cheering the president. But others said his words meant little.

“These are the same promises he made last week, that he made a few years ago, that he made in 1987, but on the ground it is always the same,” one person said, declining to be identified for fear of reprisals.

Security forces fired again at crowds of demonstrators who gathered in downtown Tunis; dozens have died so far in the crackdown on the protests, and it was impossible to confirm how many more died Thursday.

In what appeared to be a sign of division within the government or its forces, the military was withdrawn from the city by the end of the day, replaced by the police and other security forces considered more loyal to the ruling party and Interior Ministry.

There were calls for a general strike on Friday, and some people said they expected the protests to escalate when large groups of Tunisians spilled into the streets from their mosques after Friday Prayer. The government has shut down schools, universities and trains running to and from the city, leaving crowds of young people idle and many people with no way to get home.

Throughout a month of demonstrations, protesters have relied on Facebook and other social media to advertise and coordinate their actions, which started after a college-educated street vendor in a small provincial town burned himself to death in despair. (The police had confiscated his wares for lack of a permit.)

On Thursday morning a Facebook group called “The people of Tunisia are setting themselves on fire Mr. President” announced, in Arabic: “Today Hammamet: With our blood, with our souls, we sacrifice ourselves for the martyr.”

By midday, hundreds of young men were in the streets of this coastal resort city. Several banks were in flames, including one adjacent to the police station. Some said that clashes with the police had begun here on Wednesday and that they had turned out to avenge the deaths of two protesters killed the day before.

Just as in other protests in recent days, the demonstrators called for President Ben Ali to step down. But many seemed even more angry at his second wife, Leila Trabelsi, and her family — “No, no to the Trabelsis who looted the budget,” has been a popular slogan — and some said they still considered the president a good man brought down by the greed of his wife and her clan. Many refer to the president’s extended relations simply as The Family or The Mafia.