CAIRO — Egypt plunged deeper into political crisis just eight days before elections, as security forces attacked protesters Sunday in unrest that appears headed toward a second uprising, this time against Egypt's military rulers.

Egyptian soldiers and police set fire to protesters' tents in Cairo's Tahrir Square, the nerve center of the revolt that brought down President Hosni Mubarak and left the military in charge of Egypt.

Police fired tear gas and rubber bullets at demonstrators demanding that the military rulers quickly transfer power to a civilian government. At least 11 protesters were killed and hundreds were injured after a second day of clashes in some of the worst violence since the uprising ended Feb. 11.

Many compared the breadth and intensity of the new battles for the square — the iconic heart of the Arab Spring — to the early days of the uprising against Mubarak, only this time the target was the ruling military council's leader, Field Marshal Mohamed Hussein Tantawi.

Clashes and civil disobedience continued in Alexandria, Suez and other big cities as protesters expressed their solidarity.

Egyptians worried that the violence would force a delay in parliamentary elections and leave the ruling military council in power even longer.

Under the plan now, the new parliament will be accountable to the military council until a full transfer of power to civilian control occurs when a president is elected late next year or in 2013.

The military council expressed "deep regret" over the violence and said the interim government would take unspecified "urgent measures" to restore calm before the elections begin, according to the council's official Facebook page. The statement did not respond to protesters' demands, which also included a revised timetable for elections, but denied it was trying to cling to power.

Caretaker Prime Minister Essam Sharaf and the military council met for crisis talks, but one of the senior generals said there would be no delay of elections, set to begin Nov. 28.

However, Culture Minister Emad Abu Ghazi, resigned from the council in protest of the military's tactics. Protesters were furious the Cabinet also announced its support of the Interior Ministry, which oversees the riot police.

Until this weekend, the black-clad Interior Ministry police, who were a hated symbol of Mubarak's regime, had largely stayed in the background while the military took charge of security.

The clashes have turned parts of downtown Cairo into a war zone covered in a thick fog of tear gas and strewn with empty gas canisters and rocks. As in the earlier uprising, protesters established lookouts and a whistle system to alert when security forces were coming.

Some protesters collapsed on sidewalks from the gas. Others were carried to alleyway field clinics for treatment of broken bones, birdshot wounds and burns from searing tear-gas canisters.

Tareq Salem, a volunteer physician, said doctors at one clinic had treated more than 1,000 protesters in the past two days. The health ministry said 53 security officers were injured during that time.

At dusk Sunday, military police stormed into the square and cleared it within minutes, beating protesters and destroying their tents. The operation was broadcast live on television. Then the forces pulled back, and the protesters returned.

"They were not just dispersing us, they were beating us wildly and burning all the tents and banners in the square," said Abdalla Saadawi, a protester who was told by field doctors that he has a mild concussion.

He was bleeding and needed to get to the hospital, but there were no ambulances or taxis in the dark, debris-littered streets.

A handful of politicians suspended their election campaigns in solidarity with the demonstrators. Egypt's first female presidential candidate, Bouthaina Kamel, was briefly arrested in the melee, her family said in online posts.

Egypt's influential Islamists — the conservative Muslim Brotherhood and some of the more fundamentalist Salafis — allowed their members to join the battles but didn't issue a formal call to do so, which many activists interpreted as an attempt to play both sides at this sensitive time.

The Islamists can say they had a presence in the square, but their politicians will focus on campaigning and not alienating the many voters who disapprove of the continued demonstrations. Islamists, the best-organized political force, are expected to do well in the parliamentary polls.

"The Muslim Brotherhood not showing up and joining the sit-in was expected. All they need is for the elections to happen so they can gain seats in the parliament," said Ahmed Maher, leader of the liberal April 6 Youth Movement, which was instrumental in the anti-Mubarak uprising.

Maher said there were exceptions. Two Islamist presidential candidates, Muslim Brotherhood youth activists and Salafis who defied their clerics joined the demonstrations.

"It's very apparent that there will be no security during the coming elections," said Mahmoud Fathy, a candidate from the Salafi Fadila Party, which supports the protesters but opposed the idea of a long-term sit-in. "If they use such force and agitate the public over a minor legitimate protest, how would they control a nationwide electoral process?

"I am warning every member of this Cabinet and military council against any attempt at postponing or canceling elections, because it would lead to very regrettable consequences — public disobedience, civil war, you name it," said Fathy, who joined the protesters in the square.

The protesters' suspicions about the military were fed by a proposal issued by the Cabinet last week. It would shield the armed forces from any civilian oversight and give the generals veto power over legislation dealing with military affairs.

But other concerns are also feeding the tensions on the street. Many Egyptians are anxious about what the impending elections will bring. They worry that stalwarts of Mubarak's ruling party could win a significant number of seats in the next parliament because the military did not ban them from running for public office, as requested by activists.

The military's failure to issue such a ban has fed widely held suspicion that the generals are reluctant to dismantle the old regime, partly out of loyalty to Mubarak, their longtime mentor.

Additional information from The Associated Press, Los Angeles Times and The New York Times