US Ambassador Chris Stevens and three other Americans were killed in Libya Tuesday in an attack by Muslim extremists on the US Consulate in Benghazi.

The protesters said they were angry over a film they said ridiculed the founder of Islam, the Prophet Mohammed.The film was produced by an Israeli-American real estate developer, with expatriate members of Egypt’s Christian minority who are residents in the United States.

The mob set fire to the building during the attack, witnesses and officials said. Rocket-propelled grenades (RPGs) were fired at the consulate from a nearby farm.

The Libyan attack came in the wake of a protest in which demonstrators waving black banners stormed the U.S. Embassy in Cairo, tore down the American flag and torched it. At least 2,000 people stood at the foot of the walls surrounding the embassy as about 20 of the rioters scaled the walls.

Rioters also drew anti-American graffiti on the wall and demanded that the United States end its presence in Egypt. U.S. soldiers prevented the rioters from entering the Embassy compound. Witnesses said that Egyptian police at the scene did litttle to stop the rioters’ advance to the Embassy walls, which are usually cordoned off.

Just prior to the attack, the U.S. released a statement saying: “The Embassy of the United States in Cairo condemns the continuing efforts by misguided individuals to hurt the religious feelings of Muslims – as we condemn efforts to offend believers of all religions. Today, the 11th anniversary of the September 11, 2001 terrorist attacks on the United States, Americans are honoring our patriots and those who serve our nation as the fitting response to the enemies of democracy. Respect for religious beliefs is a cornerstone of American democracy. We firmly reject the actions by those who abuse the universal right of free speech to hurt the religious beliefs of others.”

Both attacks occurred on the anniversary of the September 11, 2001 multi-site attacks on America by the international Al Qaeda terrorist organization. In that operation, four airliners were hijacked and destroyed while being used to kill more than 3,000 people. The Twin Towers of New York City’s World Trade Center were destroyed, the Pentagon building was damaged and the citizens of the United States were attacked on their own soil for the first time in decades.