Angry Egyptian demonstrators climbed the walls of the U.S. Embassy in Cairo and tore down the American flag in protest of a film they say is offensive to Islam's Prophet Muhammad.

Some 2,000 demonstrators, largely ultra conservative Islamists, gathered at the embassy Tuesday. Witnesses say the demonstrators tried to raise a black flag with the words “There is no God but Allah and Muhammad is his messenger” in place of the U.S. flag.

It was not immediately clear what film had angered the group. However, some media reports credit a film allegedly financed by expatriate members of Egypt's Coptic Christian minority group.

There were no reports of clashes or injuries.