Protests against a trailer for a film insulting to Islam show no sign of abating as the unrest targeting Western embassies continue for a fifth day.
Latest reports say one person has been killed and more than two dozen wounded in clashes between police and protesters near the U.S. Embassy in central Cairo.
At least four people -- all protesters -- have been killed and dozens more wounded in demonstrations in more than 20 countries from the Middle East to Southeast Asia since they erupted on September 11.
Most rallies have been peaceful, but they turned violent in several capitals, in particular in Tunisia and in Sudan.
An elite U.S. Marine force arrived in Yemen's capital, Saana, where security forces battled with a large crowd trying to march on the U.S. Embassy.
Meanwhile, caskets with the remains of four diplomats, including the U.S. ambassador to Libya, arrived back in the United States.
Speaking at a military base outside Washington, U.S. President Barack Obama said on September 14 that justice would be served to those who killed Ambassador Chris Stevens and the three other Americans when the U.S. Consulate in Benghazi was overrun and set ablaze by armed individuals.
He added one day later that there was no justification for attacks on U.S. embassies by crowds angered by the film.
"I have made it clear that the United States has a profound respect for people of all faiths. We stand for religious freedom. And we reject the denigration of any religion -- including Islam," Obama said in a weekly radio address. "Yet there is never any justification for violence."
Secretary of State Hillary Clinton called the deaths of the four Americans "senseless" and "unacceptable."
"The people of Egypt, Libya, Yemen, and Tunisia did not trade the tyranny of dictator for the tyranny of a mob," Clinton said on September 14. "Reasonable people and responsible leaders in these countries need to do everything they can to restore security and hold accountable those behind these violent acts."
In Tehran, Iranian Supreme Leader Ayatollah Ali Khamenei called on the United States to punish the producers of the video.
The Obama administration has condemned the video, which shows the Prophet Muhammad as a womanizer, cheat, and pedophile.
There are still questions about the filmmaker, whom many reports suggest
could be a 56-year-old, Egyptian-born Coptic Christian with a criminal record who lives in California and operates under a handful of pseudonyms, including Sam Bacile.
U.S. federal police are meanwhile investigating the activities of the man
, Nakoula Basseley Nakoula, who has previously been convicted of financial crimes. A Los Angeles County Sheriff's spokesman says Nakoula was taken by police officers from his home early on September 15 for voluntary questioning by federal probation officers.
Nakoula, who was convicted in 2012 of bank fraud, was banned from using computers or the Internet without permission as part of his sentence.
A trailer of the film uploaded to YouTube months ago was dubbed into Arabic by an Egyptian cleric in early September, setting off the firestorm of anger among Muslims.
Based on reporting by dpa, Reuters, and AP