Protesters in Egypt and Libya attacked U.S. diplomatic missions on Tuesday, leading to the death of an American staffer at the consulate in the Libyan city of Benghazi after fierce clashes at the compound, a Libyan official said.

"One American staff member has died and a number have been injured in the clashes," Abdel-Monem Al-Hurr, spokesman for Libya's Supreme Security Committee, said, adding he did not know the exact number of injured or what the cause of death was.

The violence in Benghazi followed protests in neighboring Egypt where protesters scaled the walls of the Cairo embassy and tore down the American flag and burned it during protests over what demonstrators said was a U.S. film that insulted the Prophet Mohammad.

On Tuesday, Egypt's prestigious Al-Azhar mosque and seat of Sunni learning condemned a symbolic "trial" of the Prophet organized by a U.S. group including Terry Jones, a Christian pastor who triggered riots in Afghanistan in 2010 by threatening to burn the Koran.

Jones said that on Tuesday's anniversary of the September 11, 2001, attacks on the World Trade Center and the Pentagon, he had released a video promoting a film that portrayed the Prophet in a "satirical" manner. Many Muslims consider any depiction of the Prophet offensive.

Gunmen in Benghazi attacked the compound on Tuesday evening, clashing with Libyan security forces, officials said. "There is a connection between this attack and the protests that have been happening in Cairo," Hurr said.

The U.S. State Department did not refer to any deaths, but said in a statement: "We can confirm that our office in Benghazi, Libya, has been attacked by a group of militants. We are working with the Libyans now to secure the compound. We condemn in strongest terms this attack on our diplomatic mission."

Among about 2,000 protesters gathered in the Egyptian capital was Ismail Mahmoud, who, like others, did not name the film that angered him, but called on President Mohamed Morsi, Egypt's first civilian president and an Islamist, to take action.

"This movie must be banned immediately and an apology should be made," said the 19-year-old Mahmoud, a member of the "ultras" soccer supporters who played a big role in the uprising that brought down Hosni Mubarak last year.

Once the U.S. flag was hauled down in Cairo, some protesters tore it up and displayed bits to television cameras. Others burned the remnants outside the fortress-like embassy building in central Cairo. But some protesters objected to the flag burning.

BENGHAZI CLASHES

In Benghazi, Reuters reporters on the scene could see looters raiding the empty U.S. consulate's compound, walking off with desks, chairs and washing machines.

Unknown gunmen were shooting at the buildings, while others threw handmade bombs into the compound, setting off small explosions. Small fires were burning around the compound.

Passersby entered the unsecured compound to take pictures with their mobile phones and watch the looting.

No security forces could be seen around the consulate and a previous blockade of the road leading to it had been dismantled.

"The Libyan security forces came under heavy fire and we were not prepared for the intensity of the attack," Hurr said.

In Washington, a U.S official who spoke on condition of anonymity said, "We have no reason to believe, at this time, that the Cairo protests and the attack in Benghazi are connected in motive."

Libya's interim government has struggled to impose its authority on a myriad of armed groups that have refused to lay down their weapons and often take the law into their own hands.

A number of security violations have rocked Benghazi, Libya's second biggest city and the cradle of last year's revolt that toppled Muammar Gaddafi.

The breaching of the U.S. Embassy walls in Cairo comes at a delicate time in U.S.-Egyptian relations, and as the United States appeared to be easing its caution over Mursi.

Last week, U.S. officials said they were close to a deal with Egypt's government for $1 billion in debt relief. Washington had also signaled its backing for a badly needed $4.8 billion loan that Egypt is seeking from the International Monetary Fund.

"I would urge you not to draw too many conclusions because we've also had some very positive developments in our relationship with Egypt," State Department spokeswoman Victoria Nuland said.

"One of the things about the new Egypt is that protest is possible," she said. "Obviously we all want to see peaceful protest, which is not what happened outside the U.S. mission, so we're trying to restore calm now."

Washington has a large mission in Egypt, partly because of a huge aid program that followed Egypt's signing of a peace treaty with Israel in 1979. The United States gives $1.3 billion to Egypt's military each year and offers the nation other aid.

Following the protest, Egypt's Foreign Ministry said it was committed to giving all embassies the protection they needed.