CAIRO — An Egyptian court on Monday banned the Muslim Brotherhood and its vast social services network in what could be a devastating blow to the Islamist organization, which swept Mohamed Morsi to the presidency just last year and has fiercely resisted the military coup that ousted him in July.

The far-reaching ruling appears to apply to any group remotely associated with the world’s oldest Islamist movement, granting temporary legal cover to the military-backed government of Gen. Abdel Fatah al-Sissi to broaden a crackdown that has already left the Brotherhood battered.

Hundreds of Muslim Brotherhood supporters have been killed and thousands have been arrested, including Morsi and other top leaders. Authorities have lately reached inside mosques to bar thousands of Islamist-leaning preachers.

The ban covers “all the activities of the Muslim Brotherhood organization, the groups emerging from it, its associations, and any institution that branches from it or follows the group or receives financial support from it,” according to Egypt’s state media outlet, MENA, which offered the only account of a ruling that has not been made public.

State Department spokeswoman Jen Psaki said Monday that U.S. officials are seeking further details about the ruling, and she urged all parties to “avoid steps that would undermine” an inclusive political process.

Monday’s ruling is likely to fuel the anger that has begun to erupt in the form of attacks on police and security forces in Egypt’s eastern Sinai region, in its Nile Delta towns and in the heart of Cairo, where a suicide bomber early this month targeted the country’s interior minister, who escaped unhurt.

What’s behind the ruling?

As a legal matter, however, experts were unsure whether the ruling was indeed part of an orchestrated attempt to target the Brotherhood’s financial and organizational empire. Some speculated that the judge — a low-level jurist at the obscure Court of Urgent Matters — was simply trying to please a regime that has relentlessly demonized the Brotherhood as “terrorists.” Other court cases and decisions may modify or reverse Monday’s ruling.

But at least for now, the ruling gives authorities even more power to pursue a group that had been banned under a series of Egyptian autocrats, only to emerge as the core of the country’s new leadership — if only briefly — after last year’s elections.

“It is giving the government the broadest possible mandate to start sifting through all kinds of organizations and entities and freeze assets belonging to the Brotherhood,” said Hossam Bahgat, director of the Egyptian Initiative for Personal Rights. “It’s yet another tool in the box of the mastermind behind the current crackdown on the Brotherhood.”

Since the July 3 coup, Egyptian security forces have arrested nearly all of the Brotherhood’s top leaders. They have been charged with murder, inciting violence and other crimes that the group’s supporters contend are fabricated.

Monday’s ruling allows security forces to go still further, targeting the Brotherhood’s network of health clinics, schools and other social services, all of which have made the group enormously popular among millions of poor Egyptians.