At least five people were killed on Friday in demonstrations over a film made in the US that mocks Islam - as protests spread around the world.
In Tunisia, three people were killed after crowds breached the US embassy compound in the capital Tunis.
The US embassy in Khartoum was also attacked, and one person was killed. There were further clashes in Yemen and Egypt. One person died in Lebanon.
Protests began on Tuesday against the film, Innocence of Muslims.
It depicts the Prophet Muhammad as a womaniser and leader of a group of men who enjoy killing. Clips were distributed online with an Arabic voice-over.
The film's exact origin and the motivation behind its production remain a mystery.
In Khartoum, a crowd of several thousand attacked the US embassy. At least one person was killed.
The crowds gathered first outside the German embassy, setting it partially alight and causing extensive damage.
The UK embassy nearby was also targeted by protesters but escaped major destruction.
The controversial film has no known links to either Germany or the UK.
Both countries confirmed all their staff in their Khartoum embassies were safe.
"I condemn in the strongest possible terms today's attack and call on the Sudanese authorities to ensure that those involved are brought to justice," said UK Foreign Secretary William Hague.
In Tunis, hundreds of protesters entered the embassy compound and set fire to several vehicles in the car park.
Police fired shots, but it was not clear whether these are rubber bullets or live rounds.
Demonstrators raised a black flag bearing the Islamic proclamation of faith: "There is no god but Allah and Muhammad is his messenger."
The American school in Tunis was also set on fire.
In Cairo, police firing tear gas pushed about 500 protesters back from the US embassy. Streets nearby were blocked with barbed wire, concrete and police vehicles.
Islamist groups and others had called for a peaceful "million-man march" in the city, but a number withdrew those calls on Friday.
The Muslim Brotherhood of Egyptian President Mohammed Mursi said it would organise marches and sit-ins in front of mosques - but none outside the US embassy in Cairo.
After talks with Italian leaders in Rome, Mr Mursi reiterated his government's determination to protect foreign diplomats on its soil. He also condemned the film as unacceptable.
Later on Friday, Islamic militants attacked an international observer post in Egypt's restive Sinai region.
The base is not far from the border with Gaza and Israel. It houses some 1,500 members of the multinational force, including American troops.
In other developments:
In the Yemeni capital Sanaa, security forces fired warning shots and water cannon to disperse protesters near the US embassy
The US is sending a fast-response team of 50 marines to Sanaa to boost security
In the Lebanese city of Tripoli, protesters set fire to a KFC fast-food restaurant, sparking clashes with security forces
In Bangladesh, thousands of demonstrators demanded harsh punishment for the film's makers, and burned the American flag
In London, about 200 protesters gathered outside the US embassy, burning the US and Israeli flags but there was no violence
About 1,000 people joined a protest in the eastern Afghan city of Jalalabad, burning an effigy of US President Barack Obama
The US embassy in Brussels has been evacuated
Thousands of Palestinians demonstrated in the Gaza Strip and East Jerusalem
In Nigeria, police in the flashpoint northern city of Jos fired live rounds at a protest outside a mosque
There were also protests in eastern Sri Lanka and in the Maldives
The protests against the film began on Tuesday in Cairo.
They spread to the Libyan city of Benghazi, where demonstrators stormed the US consulate, killing the ambassador and three other Americans.
President Obama and Secretary of State Hillary Clinton are to attend a ceremony at Andrews Air Force Base for the return of the remains of the Americans killed.
The US has said it is stepping up security at its diplomatic missions around the world in the wake of the attack.
The BBC has been told that the US consulate in Benghazi was not given the standard security contract offered to most US diplomatic missions in the Middle East.
The allegation came from Western private military contractors.
A White House spokesman has said there was no "actionable intelligence" in advance about the Benghazi attack.
President Obama has now ordered a review of security at US diplomatic facilities around the world.