CAIRO -- Egypt's military-backed government on Wednesday designated the Muslim Brotherhood a terrorist organization, criminalizing the activities and finances of a movement that rose to power in national elections last year but has been crippled by a government crackdown since a coup in July.
The announcement was a stunning blow to the decades-old Islamist organization, which survived for years in the shadows and in prison cells under then-President Hosni Mubarak but rose to the height of political power after his ouster in the 2011 uprising.
With the victory of Mohammed Morsi -- a former Brotherhood leader -- in Egypt's first democratic presidential election in 2012, the movement was poised to realize its Islamist project but struggled to govern the country's vast and bloated bureaucracy.
Morsi's presidency faltered under an already crumbling economy and his controversial efforts to pass a new national constitution, further isolating the increasingly unpopular Brotherhood, whose leaders began courting hard-line Islamists to bolster support.
Egyptian legal experts said the decree would shutter hundreds of charities and non-governmental organizations affiliated with the Brotherhood, one of Egypt's largest opposition groups. The organizations provide health care and other services to rural and urban areas that lack infrastructure.
Anyone who is a member of the Brotherhood, participates in its activities or promotes or funds the group will be subject to prosecution under the Egyptian penal code, analysts said. Membership in a terrorist group is punishable by five years in prison. The maximum penalty for providing weapons and ammunition to a domestic terrorist group is death.
Brotherhood officials could not be reached immediately for comment. But a statement posted on the group's official Twitter account called Wednesday's declaration a "worthless decision from an illegal gov't without any evidence and will not change anything in reality."
"The protests are in the streets despite a law restricting them -- and killings and prison sentences. All this has not changed the will of the people," said Ibrahim Elsayed, a member of the Brotherhood's political group, the Freedom and Justice Party, The Associated Press reported. "The decision has no value for us and is only worth the paper it is written on."
The declaration by Egypt's interim cabinet seems likely to harden further the divide between Morsi's supporters and secular backers of the temporary government ahead of a referendum on a new constitution scheduled for next month.
After the announcement, the United States expressed concern about "the current atmosphere and its potential effects on a democratic transition in Egypt."
"We think it is essential for Egypt to have an inclusive political process; it is the best means of restoring the stability that the Egyptian people want and that is necessary to the country's economic recovery," State Department spokeswoman Jen Psaki said. "There needs to be dialogue and political participation across the political spectrum."
The government acted quickly to blame the Brotherhood -- which renounced violence decades ago -- for a deadly car bombing Tuesday outside a security headquarters building in the Nile Delta city of Mansoura. The allegation has inflamed tensions and given rise to vigilante attacks against Brotherhood supporters.
Founded in 1928, the Muslim Brotherhood was banned by Egyptian President Gamal Abdel Nasser after an attempt to assassinate him in 1954. With grass-roots appeal, the movement survived several subsequent crackdowns.
Deputy Prime Minister Hossam Eissa accused the Brotherhood of carrying out the Mansoura attack and said, in response, the government had decided to classify the organization as a terrorist group. Eissa did not provide evidence the Brotherhood was involved in the bombing or any other recent attacks on security forces in Egypt.
On Wednesday, a Sinai-based jihadist group, Ansar Bayt al-Maqdis, or Ansar Jerusalem, claimed responsibility for Tuesday's bombing, which killed 15 people, including 11 police officers, in one of the deadliest such attacks in Egypt in years.
Analysts say the group, which surfaced in Egypt's restive Sinai Peninsula in 2012, is probably responsible for most of the more complex sophisticated operations against security compounds in Egypt since the military coup. The group has claimed responsibility for several major car bomb attacks in Egypt in recent months, including an attempt to assassinate the interior minister in a Cairo suburb in September.
In the statement released to jihadist forums Wednesday, Ansar Bayt al-Maqdis warned Egyptian police and soldiers to abandon their posts and stop working for the government "to preserve their religion and lives."
In Mansoura on Wednesday night, anti-Islamist crowds roamed the streets and burned and looted Brotherhood-linked businesses. Residents chanted against the Islamists in the street, and others played pro-military songs.