Politicians have condemned the violence as Islamist riots that began in Libya earlier this week have spread to other parts of the Arab world.

Protesters attacked the US embassies in Cairo and Benghazi on Monday evening, allegedly in response to the circulation of a low-budget film denigrating the P rophet Mohammed, in riots that led to the deaths of US envoy Christopher Stevens and there other embassy staff members in Libya.

In the last few days demonstrators have taken to the streets in other parts of the region, including Lebanon, where the pope is on a visit, and in Bangladesh, where protesters were witnessed setting fire to the American and Israeli flags.

In Jerusalem around 400 Palestinians attempted to storm the US consulate.

Elsewhere, in Yemen, Sudan and Pakistan , thousands of anti-Western protesters took to the streets and tried to breach embassy buildings, in scenes that commentators have warned are being exploited by radical Islamist groups.

In Tripoli, buildings including a branch of the US chain KFC were stormed, with protesters setting fire to them. One person was reported to have died during the riot.

The video, which was made by a Coptic Christian who initially falsely claimed to be an Israeli Jew, is called "Innocence of Muslims" and presents the Prophet as a womaniser and child molester.

Egyptian president Mohammed Morsi, who is from the Muslim Brotherhood Party, addressed protesters, saying: "It is required by our religion to protect our guests and their homes and places of work. So I call on all to consider this, consider the law, and not attack embassies, consulates, diplomatic missions or Egyptian property that is private or public."

President Obama, in a strongly-worded statement, reminded those stirring up trouble that "no act of terror will go unpunished".

He told supporters at a campaign event: "I will not dim the light of the values that we proudly present to the rest of the world. No act of violence shakes the resolve of the United States of America."

"There is no justification, none at all, for responding to this video with violence," added US Secretary of State Hillary Clinton. "We condemn the violence that has resulted in the strongest terms."

"Nothing justifies such killings and attacks," said UN Secretary-General Ban Ki-moon, adding that "at this time of rising tensions", he called for calm and restraint, and stressed the need "for dialogue, mutual respect and understanding".