Western countries have appealed for an end to violent protests targeting their embassies, sparked by a film mocking the Prophet Muhammad.
The EU urged leaders in Arab and Muslim countries to "call immediately for peace and restraint".
The US is sending marines to defend its embassy in Khartoum and has called on Sudan to protect foreign diplomats.
At least seven people died in protests in Khartoum, Tunis and Cairo on Friday and there are fears of further unrest.
Protests in Egypt have spread, with demonstrators breaking into a base holding multi-national peacekeepers in Sinai, and clashes outside the American consulate in the coastal city Alexandria.
In Afghanistan, the Taliban said their attack on the huge Camp Bastion Nato base, in which two US marines were killed, was carried out in response to the film.
US embassies have borne the brunt of the attacks after clips of the film - which was made in the US - were distributed online.
Marines were deployed to Libya on Wednesday after the attack that killed the US ambassador and three other Americans and to Yemen on Friday after violence in Sanaa.
On Friday, US Vice-President Joe Biden called his Sudanese counterpart, Ali Osman Taha, to express concern over the security of the US and other Western embassies in Khartoum.
"Vice-President Biden reaffirmed the responsibility of the government of Sudan to protect diplomatic facilities and stressed the need for the government... to ensure the protection of diplomats in Khartoum," a White House statement said.
A crowd of several thousand attacked the US embassy in Khartoum on Friday, and state radio said three protesters had been killed in clashes with security forces.
The German and UK embassies in Khartoum were also attacked, although the controversial film has no known links to either country.
European Commission President Jose Manuel Barroso condemned the attacks as unacceptable and against "the rules of the civilised world."
EU foreign policy chief Catherine Ashton urged "national authorities in all countries concerned to swiftly ensure the security of diplomatic missions and protect diplomatic staff".
"It is vitally important that leaders across the affected regions should call immediately for peace and restraint, as has already been the case in many countries."
German Foreign Minister Guido Westerwelle said the Sudanese ambassador in Berlin had been summoned on Friday and "unequivocally reminded of his government's duty to protect diplomatic missions".
Protests against the film - Innocence of Muslims - began on Tuesday in the Egyptian capital Cairo.
The film depicts the Prophet Muhammad as a womaniser and leader of a group of bloodthirsty men.
However, its exact origin and the motivation behind the film's production are still unclear.
A man suspected of involvement in its making, Nakoula Basseley Nakoula, is being questioned by federal probation officers in California.
Nakoula, who was jailed for bank fraud in 2010, is not allowed under the terms of his release to access the internet or to use aliases without permission.
He has denied involvement in the film.
Two people were killed in Tunisia on Friday after crowds breached the US embassy compound in Tunis and clashed with riot police.
The nearby American school was looted and set on fire. There was also one death during protests in Egypt and another in Lebanon.
On Friday, US President Barack Obama and Secretary of State Hillary Clinton attended a ceremony at Andrews Air Force Base for the repatriation of the Americans killed in Benghazi.
Mr Obama said the US would "stand fast" against the violence at its diplomatic missions.
Source: BBC News