CAIRO, Egypt — Egypt's military said Monday that it will give the country's rival political forces 48 hours to resolve the current political crisis, or it will intervene with a roadmap for the nation's future.

The statement was read and broadcast live on state television.

Sixteen Egyptians were killed and hundreds more injured after a day of mass protests nationwide Sunday gave way to violent clashes outside the ruling Muslim Brotherhood headquarters in Cairo overnight.

Millions took to the streets in Cairo and other cities — in demonstrations that dwarfed the protests of the uprising two years ago — to call for President Mohamed Morsi, a former Brotherhood leader, to step down after a turbulent year in power.

As night fell, demonstrators besieged the Islamist movement’s headquarters — throwing rocks and Molotov cocktails, to which Brotherhood members holed up inside responded with gunfire, witnesses said. Eight peopled were killed in ensuing clashes, and protesters eventually ransacked and looted the office, according to the health ministry.

On Monday afternoon, four ministers — of tourism, parliament, telecoms and environment — resigned from Morsi’s cabinet in protest in the unrest, Reuters reported.

But the embattled leader appeared defiant in the face of countrywide mobilization against his rule, refusing to make concessions. The president’s supporters also mounted their own protest in Cairo Sunday.

Communicating through a spokesman Sunday, Morsi called instead for talks with the opposition. "The presidency is open to a real and serious national dialogue," spokesman Ehab Fahm said. So far, political forces have refused to sit down together to negotiate.

Egyptians came out to Cairo’s Tahrir Square, and the presidential palace in the Cairo suburb of Heliopolis, to protest myriad grievances.

Morsi has failed to avert Egypt's economic nosedive, or take serious steps to reform the country’s hated police force, some protesters said.

Others were angry that the popularly elected president has encouraged what they say is a dangerous level of political polarization, in addition to attempting to turn state institutions into Brotherhood fiefdoms.

“We thought the revolution would bring some hardships, but we also thought it would bring democracy,” said real estate manager, Hassan Shanabd, as he stood outside the presidential palace Sunday.

Crowds gathered not just at the palace, but also in central squares, on street corners and outside government facilities. “Leave!” they chanted, waving red cards to symbolically reject the president’s rule. sky. Some demonstrators cheered as military helicopters flew overhead.

“Morsi was elected fairly and in a democratic way, but he’s not the one whose ruling now,” Shanabd said. “It’s the Muslim Brotherhood and their Supreme Guide. That’s the scary thing. They’re not accountable to us. Where are the checks and balances?”

In the year since he took office, Morsi undertook a series of steps critics say points to his desire to consolidate power. In November, he issued a decree that placed his decision outside judicial oversight, then moving to push through a hastily drafted constitution.

As opposition to his rule intensified, Morsi repeatedly extended what his opponents say are lukewarm officers of reconciliation talks.

Some speculated that Morsi would appoint Defense Minister Abdel Fattah Al Sisi as prime minister in a bid to temper calls for a military takeover. Fahmy, the president’s spokesman, denied the rumors.

Outside the presidential palace, protesters chanted: “Come on down, Sisi, Morsi is not my president!”

At the pro-Morsi rally a few miles away, the president’s supporters said the crowds in Tahrir were holdovers from the era of ousted President Hosni Mubarak, and that they were enemies of the revolution.

“If you go down there, you’ll find them carrying Mubarak’s mottos,” said Mohamed Sherif Abdeen, a computer teacher who was acting as a protest security guard.

After police forces announced they would not guard the party offices of the Muslim Brotherhood, Morsi supporters armed themselves to defend against any attacks.

“We’re seeing a revolution against the revolution,” Abdeen said, holding a black leather baton. “We won’t do anything if the army and the police protect government facilities. But if they do not, we will protect the president’s legitimacy with our lives.”

Not everyone in the streets wants the army to again rule the country. Sections of the crowds also carried flags carrying the names and faces of revolutionary martyrs killed under military rule, which lasted for just over one year following Mubarak's ouster.

Elsewhere, five people were shot dead in towns south of Cairo, one each in Beni Suef and Fayoum and three in Assiut.

Regardless, the demonstrations were some of the largest Egypt has ever seen.

“This makes for a different type of configuration if the size and relative peacefulness can be maintained,” Nathan Brown, a longtime Egypt scholar and professor at George Washington University, said of the protests.

“While you could previously portray the situation as one where a strong, organized Islamist movement was challenged by a disorganized but increasingly popular opposition, it’s now possible to portray this as a society rising up in rebellion against the president,” he said.

“It would seem very difficult for Morsi to hold on, or at least to ignore the protests, without making significant concessions.”



