CAIRO — Protesters in Libya and Egypt stormed U.S. diplomatic missions Tuesday on the 11th anniversary of the Sept. 11 terrorist attacks in a day of rage that underscored the growth of fundamentalist movements in countries where new governments were swept to power in the aftermath of last year’s Arab spring.

In Cairo, thousands of demonstrators stormed the U.S. Embassy, lowered the American flag and destroyed it, then danced atop the walls in a protest that lasted hours. Egyptian police made no effort to confront them.

In Libya’s second largest city, Benghazi, protesters stormed the U.S. consulate, setting the building ablaze. Witnesses said they heard loud explosions nearby and that armed men had surrounded the area around the consulate, blocking the road and making it impossible for reporters to film the scene.

One man in Benghazi, who didn’t want to be identified for security reasons, suggested that Islamists were responsible for the attacks. In recent weeks, Islamist fundamentalists have destroyed cemeteries and mosques in Libya associated with the moderate Sufi strain of Islam.

“I was stopped by a guy whose beard extended to his knees,” the man said, in an exaggeration. “And he told me very proudly not to pass because we have burned the American consulate.”

In Cairo, police surrounded the embassy building but made no move to confront the demonstrators as they sprayed graffiti on the 12-foot walls that encircle the compound. One protester tested his spray can on a policemen’s shield before aiming it at the wall; the officer simply shrugged.

The police also made no move to challenge the protesters as they lowered the American flag. As the flag was torn and then set on fire, a man climbed a ladder alongside the flagpole and replaced the flag with one that read, “There is no God but Allah and Mohammad is his messenger.”

Among the chants yelled toward the embassy was “Take a picture, Obama, we are all Osama,” a reference to Osama bin Laden, who planned and financed the 9/11 attacks and whom U.S. commandoes killed on May 2, 2011.

“Say it, don’t fear: Their ambassador must leave,” was another.

State Department officials said their employees weren’t in danger. Most had gone home early in anticipation that the protesters would scale the wall around 5 p.m.

The Egyptian protests were spurred by two controversial figures that stoked old grievances against the United States: that it is anti-Muslim and doing harm to the Muslim world. It was a reminder that Egypt’s first democratic election, which the United States encouraged, hadn’t yet yielded any change in widely held beliefs about American interests in the region.

Organizers of the protest at the embassy said they’d begun planning the event last week when a controversial Egyptian Christian activist who lives in the United States, Morris Sadek, released a trailer for a movie called “Muhammad” that repeatedly mocks the prophet and the religion. The 14-minute clip, which Sadek first posted on his Facebook page Sept 5, attacked basic tenets of the Islam and suggested that the religion had spread only because the prophet told those he encountered to “pay extortion or die” if they didn’t convert.

Christians make up roughly 10 percent of Egypt’s population, and officials from Egypt’s Coptic churches have condemned the film.

The film controversy came as a controversial Florida pastor, Terry Jones, whose burning of the Quran in 2011 set off days of rioting in Afghanistan, announced that he planned to put the prophet on trial Tuesday in what he called International Judge Muhammad Day.

In a video announcing the “trial,” Jones, wearing a black shirt with the word “Infidel” printed on it in Arabic, said that he planned to charge the prophet “with being a false prophet, thus leading 1.6 billion people astray.”

The embassy had tried to pre-empt the attack, issuing a statement hours earlier that condemned “the actions by those who abuse the universal right of free speech to hurt the religious beliefs of others.”

Nader Bakkar, a spokesman for the conservative Islamist Nour party, said he’d received a call from the embassy, apologizing, but that it wasn’t enough for him to call off the protest. Insulting the prophet “goes beyond a red line for us,” he said.

“The American people must know we do not accept any kind of insult of the prophet, peace be upon him,” Bakkar said, adding nevertheless that he opposed pulling down the American flag.

Islam forbids any depiction of Muhammad because he’s seen as someone whose greatness can’t be replicated. In documentaries about his life, he’s often portrayed as a ray of light. That someone would mock the prophet is considered blasphemous.

Sharif Abdel Meniem, 29, who helped organize the protest, said he planned the demonstrations “because the Americans did not take a real stand against” Jones’ call.

“The prophet does not have a hand in the 9/11 attacks,” he said as chanters yelled, “The prophet’s army has arrived.”

That the protest fell on Sept. 11 wasn’t lost on those participating.

“This anniversary provokes the United States,” said Islam Mustafa, 23, a student. “But (Americans) are the ones provoking us.”