©Shawn Baldwin for The New York Times

Women walking past riot police in central Cairo on Sunday.

CAIRO: The center of this normally bustling, overcrowded, traffic-clogged city was largely quiet Sunday, the roads nearly empty, many of the stores shuttered, as the riot police came out in force to prevent a general strike aimed at signaling widespread discontent with President Hosni Mubarak and his government.

Egypt has virtually no organized political opposition, except the Muslim Brotherhood, which is banned and barred from politics.

But events Sunday underscored the rise of a potentially more dangerous challenge to the government's monopoly on power: Widespread public outrage and a growing willingness by workers and professionals to press their demands by striking.

The main complaint is economic, driven by rising food prices, depressed salaries and what opposition leaders say is an unprecedented gap between rich and poor. It is hard to say if the streets were empty Sunday because people stayed home for fear of getting caught in the crossfire between protesters and police, or because of the call to stay home as a form of protest.

Either way, the government took the threat of a mass mobilization so seriously that it issued a warning to potential strikers, saying it would "take necessary and resolute measures toward any attempt to demonstrate, impede traffic, hamper work in public facilities or to incite any of this."

In Cairo, riot police officers massed in Tahrir Square, the center of the city. They stood in formation outside the lawyers', doctors' and journalists' syndicates. State security agents had visited government workers in advance and ordered them to attend work on Sunday, some workers said. At the lawyers' syndicate, a few hundred protesters stood on the roof and on a balcony chanting "Down, down Hosni Mubarak."

Hundreds of students demonstrated at three universities in Cairo.

In Mahalla al-Kobra, the center of Egypt's textile industry north of Cairo, a melee broke out late in the day as the riot police fired tear gas and workers threw stones. Officials said there were more than 200 arrests around the country, including at least seven people arrested for their efforts to use the Internet to promote the call for a day of unrest.

"I am not about to claim that the Egyptian people are finally rebelling," said Abdel Ahab El Meseery, an organizer with Kifaya, an opposition movement, who once served as the Arab League's cultural attaché to the United Nations. "The element of fear is there. The people are afraid of the government, but the government is as afraid of the people."

Under Mubarak and his governing National Democratic Party, officials have succeeded in stunting the growth and influence of political opposition. The only opposition group with a broad network and a core constituency is the Muslim Brotherhood, which has little ability to effect political change because its members are routinely arrested and jailed. Local elections are scheduled for Tuesday, and the government has arrested hundreds of Brotherhood members and supporters in advance.

The Brotherhood, struggling to regain its footing after the intense and persistent police pressure, distanced itself from the call to strike and said it would not participate.

Since September 2007 the government itself has scrambled to keep pace with the growing reliance on strikes as a tool to press worker demands. Textile workers, tax clerks and university professors have all held strikes or threatened to strike.

Doctors have also threatened to strike, complaining that physicians with 20 years experience, for example, often make no more than 450 Egyptian pounds a month, the equivalent of about $80.

"What made us take more confrontational measures is that we saw other groups doing so and making their demands," said Hamdy El Sayyid, longtime chairman of the doctors' syndicate.

But what has turned the demands of individual workers into a potential mass movement, officials and political analysts said, has been inflation on food products, mostly bread and cooking oil. The rising cost of wheat, coupled with widespread corruption in the production and distribution of subsidized bread, has prompted the president to order a resolution to the problem.

But that has done little to calm public outrage, or lower bread prices.

On Adly Street, a broad thoroughfare in central Cairo, many more stores than usual were shuttered Sunday, according to street vendors and local residents. It was a windy day, with a sandstorm and rain showers, which may have offered people added encouragement to stay off the streets.

"People are staying at home today," said Ashraf, a clerk in a luggage store on Adly Street. He was afraid to give his last name, for fear of arrest, but he said he kept his children home from school and dressed in all black as signs of support for the protest. "Because of the prices, because we can't get food," he said explaining the reason for the strike.

The strike plans began with the workers in Mahalla, who had said they would strike at 7 a.m., when workers changed shifts, to protest low wages. But state security forces arrived in mass and workers said they grew intimidated and went to work.

But the initial plan led other, smaller groups to call for the day of protest as a general sign of discontent with the direction Egypt is taking.

Kifaya, which had been in the vanguard of opposition movements until 2005, when its public following dwindled, joined the call. What may have spooked government officials mostly is the way in which technology - especially text messages on cellphones - was used to spread the word, without any formal organization promoting the call, political analysts said.

Residents of Imbaba, a conservative, poor neighborhood inside Cairo, asked neighbors to stay home as a sign of protest.

Belal Fadl, a scriptwriter and satirist in Cairo, said that Egypt was going through a very confusing time, one in which, he warned, the government should not rely on a population that is politically apathetic.

The problems, he said, were now too widespread, and too close to home.

"People in Egypt," Fadl said, "don't care about democracy and the transfer of power - they don't believe in it because they didn't grow up to it in the first place. This is unfortunately the case. Their problem is limited to their ability to survive and if that is threatened then they will stand up."

Mona el Naggar contributed reporting.