Hundreds of Yemeni demonstrators angered over a film mocking Islam have stormed the grounds of the U.S. embassy in Sana'a, continuing a wave of anti-American protests sweeping the region.

The mob torched a number of diplomatic vehicles Thursday as security guards used water cannons and warning shots in a bid to drive them out of the heavily fortified compound. A number of people were reportedly injured.

The U.S. ambassador to Libya and three of his staff were killed Tuesday after suspected Islamist militants stormed the American consulate in Benghazi.

Meanwhile, protests continued outside the U.S. embassy in the Egyptian capital, Cairo, Thursday as police used tear gas against a crowd of about 200 youth. The violence was directed against a short American-made amateur film mocking the Prophet Muhammad.

Egypt's Islamist President Mohamed Morsi, on an official visit to Brussels Thursday, slammed “attacks” on the Muslim prophet in the film, while also condemning the violence. He pledged to protect foreigners in Egypt.

Earlier, U.S. President Barack Obama and the president of Libya's National Assembly, Mohamed Magarief, agreed Wednesday to cooperate closely in investigating the deadly attack on the U.S. consulate in Benghazi. The Libyan leader has apologized to the United States for the assault.

Washington sent two Navy destroyers, a Marine Corps anti-terrorist security team and federal investigators to Libya to protect Americans and help hunt the suspected religious extremists who carried out the attack late Tuesday.

The Obama administration also ordered the evacuation of all U.S. personnel from Benghazi to the capital, Tripoli.

American officials said Wednesday the attack on the Benghazi compound and a nearby safe house may have been a planned, coordinated and complex operation, in contrast to the initial Cairo protest, which appeared to be spontaneous. They say armed militants in Libya may have used the Cairo events as cover.

But, the officials say it is too early to identify those who killed U.S. Ambassador J. Christopher Stevens and three colleagues or whether the assault was timed to coincide with the anniversary of the September 11 terrorist attacks on the United States.

American intelligence agencies are examining the alleged involvement of pro-al Qaida Ansar al-Sharia militants, but cautioned they do not have solid evidence. On Wednesday, a brigade from the group denied planning the assault.

Stevens is the first U.S. envoy to be killed on duty since 1979. He was a career foreign service officer and one of the most experienced American diplomats in the region.