UN Secretary-General Ban Ki-moon on Thursday condemned what he called the "hateful film" which is anti-Islam and touched off anti-American protest in the Middle East and North Africa, calling for calm and restraint at the time of rising tensions.

"The secretary-general is deeply disturbed by the recent violence in Libya and elsewhere in the Middle East," said a statement issued here late Thursday by Ban's spokesman. "Nothing justifies such killings and attacks."

The secretary-general "condemns the hateful film that appears to have been deliberately designed to sow bigotry and bloodshed," the statement said.

The statement came as angry demonstrations against the anti-Islam film reportedly made in the United States have spread to several countries across the Middle East and North Africa.

"At this time of rising tensions, the secretary-general calls for calm and restraint, and stresses the need for dialogue, mutual respect and understanding," the statement said.

Thursday morning witnessed the storming of the US Embassy in Yemen by several hundred protesters, reportedly still angry about the same YouTube video that sparked similar anti-American protests in Egypt and Libya earlier this week.

In Libya, where the US ambassador, Christopher Stevens, and three embassy staff, were killed during protests in Benghazi, an eastern city, on Tuesday, officials said they had made "four arrests" over the attack.

Hundreds of protesters, angered by an alleged US-made movie that insults Prophet Mohammad, broke into the US consulate building in Benghazi Tuesday night and set ablaze the building.

The US ambassador was killed along with three US embassy staff as they rushed away from the consulate building that was stormed by al Qaida-linked gunmen blaming the United States for the movie which they said insulted the Prophet Mohammad.

In the Iranian capital, Tehran, up to 500 people protested over the issue chanting "Death to America!" and death to the movie's director, reports said.

The rally, near the Swiss embassy that handles US interests in the absence of US-Iran diplomatic ties, ended peacefully two hours later, said the reports.