Egyptian security forces have confronted anti-government activists in Cairo's Tahrir Square for a third day as part of a crackdown on nationwide protests in which at least 13 people have been killed.

Security forces fired tear gas early Monday to try to clear demonstrators from Tahrir Square, where the activists had camped for a third consecutive night. Police and troops had briefly dispersed the protesters Sunday by firing tear gas and rubber bullets, but the activists retook the square later in the day. Similar confrontations erupted Sunday in the cities of Alexandria and Suez.

Authorities said Sunday's crackdowns on protests killed at least 11 people. Another two protesters were killed Saturday. Hundreds of people have been hurt, some with eye injuries from rubber bullets.

Many of the demonstrators have been chanting “The people want to topple the field marshal,” a reference to Mohamed Hussein Tantawi, leader of the Supreme Council of the Armed Forces that took power in February when a popular uprising ousted autocratic President Hosni Mubarak.

The activists accuse the military council of not moving quickly enough to return Egypt to civilian rule. They also have criticized the council for setting guidelines for a new constitution that would keep some military affairs beyond civilian control. The activists also want the military rulers to stop putting civilians on trial in military courts.

Egypt's military-backed government held an emergency meeting Sunday and promised to begin staggered parliamentary elections as planned on November 28. Some opposition activists accuse the military council of provoking the violence as a pretext for postponing the elections and extending their tenure.

The protest-related violence began early Saturday as police moved into Tahrir Square to remove hundreds of people who camped on the site after a mass anti-government rally Friday.