The protests in their 17th day — which have focused on demanding President Hosni Mubarak’s ouster and the end of his regime’s heavy hand on power — have tapped into the even deeper well of anger over economic woes, including inflation, unemployment, corruption, low wages and wide economic disparities between rich and poor.

For the second day, crowds angry over lack of housing rioted in the Suez Canal city of Port Said. On Thursday, they set fire to the local headquarters of state security, the main post office and the governor’s offices, which had already been partially burned the day before. It appeared police and soldiers were not intervening.

The spread of labor unrest was in part in direct response to calls from protesters as strikers expressed their support for the political movement. But there also seemed to be another element — locals unleashing long pent-up resentment at symbols of the state, whether it was an unpopular local police chief, a state factory seen as stiffing workers or a governor failing to follow through on promises.

The government warnings raised the prospect that the energized protests could bring a new crackdown.

Speaking to the Arab news network Al-Arabiya on Thursday, Foreign Minister Ahmed Aboul Gheit said that if "adventurers" take over the process of reform the military "will be compelled to defend the constitution and national security … and we’ll find ourselves in a very grave situation."

The night earlier, he was more explicit, saying in an interview with "PBS NewsHour" that there would be chaos if Mubarak stepped down immediately. "Do we want the armed forces to assume the responsibility of stabilizing the nation thru imposing martial law, and army in the streets?" he said. It was the second coup warning this week, with Prime Minister Omar Suleiman making similar threats Tuesday.

The warnings reflect growing government impatience as its own attempts to manage the crisis have failed. Mubarak has refused to step down immediately, saying he will serve out the rest of his term until September elections.

Suleiman has put forward a gradual program for reform in the meantime: Discussions with the opposition over constitutional amendments to be approved by referendum by June, paving the way to the election, in which Mubarak would not run.

But that outline also preserves a heavy regime hand in directing the reform process, raising suspicion it will not bring real democracy. Youth activists organizing the Tahrir protests have refused any negotiations on reform or halt to demonstrations until Mubarak goes. Not only have they fended off government attempts to fragment its ranks and draw some into talks, their protests have spread.

One of the few groups that did enter talks with Suleiman — the leftist Tagammu — announced Thursday it had broken off contacts in anger over the coup threats. Tagammu is one of the official, government-sanctioned opposition parties that have little public support and no role in the protests, and are seen by protesters as little more than extensions of the regime.

Youth activists organizing the protests planned to up the ante even further, calling for an expanded rally on Friday, hoping to repeat a showing earlier this week that drew about a quarter-million people.

Khaled Abdel-Hamid, speaking for a coalition of groups behind the protests, said they wanted Egyptians to show up at six separate rallies on main squares in Cairo from which they would all march to Tahrir Square, which has been the focal point of the demonstrations. Thousands were packing the square on Thursday, vowing not to give up until the longtime leader steps down despite a host of sweeping government concessions.

At the same time, protest organizers have made a concerted effort to bring labor movements into the protests.

The labor unrest was flaring so quickly that protesters sent out messages to railroad workers not to go on strike and halt trains because people in the provinces wanted to come to Cairo to join the Tahrir rallies.

Strikes have erupted in a wide breadth of sectors — postal workers, electricity staff and service technicians at the Suez Canal, in factories manufacturing textiles, steel and beverages and hospitals. So far, infrastructure and public services do not appear to have been affected.

But bus drivers and public transport workers announced their own strike Thursday, raising fears of paralysis in the capital, where many rely on buses and minibuses. Buses were still seen on the streets early Thursday and it’s not immediately clear how widespread the strike is.

Ali Fatouh, a bus driver in Cairo says buses were locked in the garages and won’t be moved "until we achieve our demands," which include salary increases. He says organizers are calling on all 62,000 transportation employees to participate.

If demands are not met, "we will join Tahrir, and camp there," said another bus driver, Mustafa Mohammed, who said he has been working since 1997 and only earns 550 Egyptian pounds a month, about $93. "We are immersed in debts," said Mohammed, joining a crowd outside the administration building on the outskirts of Cairo.

On Thursday, hundreds of doctors in white coats marched down a street from the Qasr el-Aini state hospital to Tahrir, chanting "Join us, O Egyptian," witnesses said.

From another direction, crowds of lawyers in black robes marched from their union to the square, waving Egyptian flags and chanting "Mubarak, you pilot, how did you get $70 billion?" — a referring to the president’s past as the air force commander.

Egyptians have been infuriated by newspaper reports that the Mubarak family has amassed billions, and perhaps tens of billions of dollars in wealth while, according to the World Bank, about 40 percent of the country’s 80 million people live below or near the poverty line of $2 a day. The family’s true net worth is not known.

"We demand a trial of Mubarak and his regime; we are protesting corruption," said Mohammed Zarie, one of the marching lawyers, who said hundreds of lawyers arrived from provinces and planned to spend the night at the square.

The labor strikes come despite a warning by Vice President Suleiman that calls for civil disobedience are "very dangerous for society and we can’t put up with this at all."

In the face of a revolt by journalists over anti-protest propoganda in state media, the pro-government head of the journalists’ union, Makram Mohammed Ahmed, said he was going on indefinite leave. The state prosecutor summoned him over lawsuits filed by journalists accusing him of "negligence" in defending journalists’ rights.

The protesters filling streets of Cairo and other cities since Jan. 25 have already posed the greatest challenge to the president’s authoritarian rule since he came to power 30 years ago. They have wrought promises of sweeping concessions and reforms, a new Cabinet and a purge of the ruling party leadership, but Mubarak refuses their demands that he step down before September elections.

U.S.-based Human Rights Watch has said about 300 people have been killed since the protests began, but it is still compiling a final toll.

The White House warned Egypt’s leaders to expect unrelenting protests unless they start to show real reforms and a transition to a freer society, dismissing governmental concessions so far as not having met even the minimum threshold of what people want.

Obama administration officials were also increasingly blunt in describing the limits of their leverage, reasserting that the United States is not seeking to dictate events in Egypt — and that it cannot.

"We’re not going to be able to force them do anything," White House spokesman Robert Gibbs told reporters Wednesday.

Still, Gibbs and other officials called on Egypt’s leaders to end the harassment of activists, to broaden the makeup of their negotiations with opposition leaders, to lift a repressive emergency law, and to take up a series of other moves the Obama government has requested for days.