Associated Press
Protesters take cover during clashes with Egyptian riot police in downtown Cairo on Sunday.

CAIRO — Egypt is frayed, bloody and slipping toward a new revolt.

The clashes that erupted for the second day in a row Sunday between police and protesters are the most volatile challenge in months to the nation's military leaders. The anger glimpsed through the tear gas and on the bruised faces of demonstrators marked a dangerous chasm between the Egyptian people and the generals who have refused to relinquish power to a civilian government.

What is unfolding in the streets of Cairo, Suez and the coastal city of Alexandria is the compounded anger over the unrealized promise of a revolution that ousted Hosni Mubarak in February but has yet to steer the country toward a new democracy. Five people have been killed across the nation, including three Sunday in Cairo's Tahrir Square, and more than 1,000 have been injured since violence broke out on Saturday.

Security forces and military police, swinging batons, firing birdshot and driving armored personnel carriers, stormed the square late Sunday afternoon, chasing out protesters and burning tents. The troops quickly retreated and growing ranks of demonstrators returned to the area, yelling epithets against the military as darkness fell. Protesters numbered as many as 20,000 before midnight.

"We are on the brink of danger. Those asking for the government to fall are asking for the state to fall," Gen. Mohsen Fangary said in a TV interview.

But at times, the military appears in denial, as if the deepening discontent against it can be placated or ignored in the run-up to next week's parliamentary elections.

The military is not ready to cede the country's future to an array of political interests, including remnants of the old regime and the dominant Muslim Brotherhood. These forces mistrust one another but they — along with thousands of idle, angry young men — have banded against what they all regard as the larger enemy in the ruling Supreme Council of the Armed Forces.

But political parties, especially Islamist groups, face a dilemma: They want to tap into the spirit of the protests but do not want violence to jeopardize the country's first significant elections in decades. The Muslim Brotherhood did not endorse the demonstrations but condemned security forces for the bloody crackdown. The ultraconservative Gamaa al Islamiya group told its followers now is "not a suitable time" to take to the streets.

"I should be at work," said Ashraf Hamed, a food vendor who joined Sunday's rally in Tahrir Square. "But I suffered from life under Mubarak, and I refuse to continue suffering and keep watching injustices being done to our revolution."

Broken glass, stones and bullet casings littered the square as about 4,000 protesters gathered while riot police battled others on side streets and protected the nearby Interior Ministry. The April 6 Youth Movement and an ultraconservative Islamist presidential candidate announced their support of the protest, but the majority of the demonstrators appeared not to belong to political parties or activist groups.

"I was against the idea of a sit-in but when I saw the police brutality against demonstrators on TV yesterday I decided to come and join them," said Adel Kassem, a university professor.