Fresh violence erupted in Egypt on Friday, as security forces clashed with Islamist protesters who had poured into the streets of Cairo for a "Day of Rage" called by the Muslim Brotherhood. At least 60 people were killed in the protests, adding to the 600-plus who died on Wednesday during the military's deadly crackdown on supporters of ousted President Mohamed Morsi.

Despite calls for calm from around the world, analysts warned that the Islamists' decision to defy the threat of force and return to the streets signaled that worse violence is yet to come. In fact, the military might have created a huge problem for itself by ousting the country's first freely elected president — with the backing of ostensibly pro-democracy liberals — because it is driving Islamists out of the electoral process and helping extremists rally support for a long-term, violent insurgency.

Already, we are seeing the beginnings of insurgent activity in the lawless Sinai Peninsula, with shadowy militants picking off security forces, as well as minority Christians, in the dead of night. "The northern Sinai Peninsula, long a relatively lawless zone, has become a dark harbinger of what could follow elsewhere in Egypt if the interim government cannot peacefully resolve its standoff with the Islamist protesters camped out in Cairo," said Robert F. Worth at The New York Times earlier this week.

And now, with Muslim Brotherhood leaders being arrested and its supporters bloodied in the streets, elements of the group could be driven underground as the country morphs into a police state, says CBS News correspondent Clarissa Ward.

"We're going to see young men who are angry who feel they cannot affect change at the ballot box," says Ward, "and that the only way to do this is through violence."

Indeed, officials in the Obama administration and other foreign governments are concerned about pro-violence factions in the Muslim Brotherhood splintering from the main group. Here's The Wall Street Journal:

While U.S. intelligence officials don't expect the Muslim Brotherhood to mount an organized insurgency in Egypt, radicals within the group could go underground and launch attacks. Some radical Islamists in Egypt who fought in Iraq during the U.S. occupation have returned home, where they could wreak havoc, officials say.

Moreover, a stockpile of arms lies in neighboring Libya, a country in which the security situation is spiraling downward in similar fashion. That impedes the ability of the Libyan government to lock down the arsenal accumulated by the late Libyan leader Moammar Gadhafi.

U.S. officials worry eastern Libya could serve as a springboard for insurgents moving across the border into Egypt. [The Wall Street Journal]

The military-backed interim government says the state of emergency it imposed will only last 30 days, and Egypt's army chief has promised to restore elected rule as soon as possible. The interim government even says it has invited the Brotherhood to join the transition, but it's hard to imagine the group making a deal now without losing the support of its base.

So, has Egypt's army made a huge mistake it will come to regret? The generals don't see it that way, suggests Michael Crowley at TIME.

However it might disturb Washington, Egypt's generals may welcome open conflict with their Islamist rivals. "The [Muslim] Brotherhood has always lost against the Egyptian military," says Gregory Aftandilian, senior fellow for the Middle East at the Center for National Policy. "So that’s the historical memory of the Egyptian officer corps: 'Whenever there was a confrontation, we've won.'"

The Egyptian military already talks as though it faces an insurgency: on Wednesday it said its crackdown had been a response to "terrorist acts" and a "criminal plan to demolish the pillars of the Egyptian state." [TIME]