CAIRO - In a remarkable turn of events, thousands of angry Egyptian women joined a fifth day of protests in downtown Cairo to voice outrage over what they said was the military's abuse and mistreatment of female demonstrators.

"Egyptian girls are a red line," they chanted during a peaceful march from Tahrir Square through the center of the Egyptian capital, while male protesters formed a protective line around them, shouting, "down with the military rule!"

Some carried posters and pictures of women they said were beaten, stripped, and assaulted in recent days, including one woman who was captured on video as military police stripped off some of her clothing to expose her bra and then appeared to stomp on her body.

The footage has been circulated widely on social media sites and around the world, fueling a growing public anger toward the Supreme Council of the Armed Forces, which has ruled the country since the overthrow in February of President Hosni Mubarak.

"That girl who was stripped by army officers didn't just reveal her body, but she revealed the brutality and atrocities carried out by the army," said one female protester. "We don't trust them anymore. They should cede power immediately."

Sensing the public frustration, the military council quickly issued an apology Tuesday and vowed to punish those responsible for the mistreatment of women. The statement expressed "deep regret to the great women of Egypt" and reaffirmed their right to protest and participate in the democratic transition.

The military's expression of regret was a stark reversal to its denials in recent days that soldiers had used excessive force against demonstrators.

On Monday, Gen. Adel Emara, a member of the military council, blamed the violence on protesters themselves, whom the army has tried to paint as criminals and vandals. At least 13 protesters have died in clashes since Friday.

In some of the harshest U.S. criticism yet of Egypt's military leaders, Secretary of State Hillary Rodham Clinton expressed shock during a speech in Washington on Monday at the treatment of female protesters.

"Women protesters have been rounded up and subjected to horrific abuse," Clinton said at Georgetown University. "This systematic degradation of Egyptian women dishonors the revolution, disgraces the state and its uniform, and is not worthy of a great people." She noted that Egyptian women played a key role in the protests that swept Mubarak from power.

The crowd seemed to grow at each step as the women in the march called up to the apartment buildings lining the streets to urge others to join - "come down, come down," they shouted in an echo of the protests that led to the ouster of Hosni Mubarak 10 months ago.

"We have to come down and call for our rights," said Sohir Mahmoud, 50. "Nobody is going to call for our rights for us."