Western nations are appealing to the Islamic world to end the violent protests against the US-produced film Innocence of Muslims.
European leaders are trying to co-operate on the issue with Arab leaders, and called for immediate peace and restraint.
While European Commission President Jose Manuel Barroso said the violence was against the rules of the civilised world, EU foreign policy chief Catherine Ashton urged Arab leaders to ensure the safety of foreign diplomats in their countries.
Protests in several countries seem be spiralling. The Egyptian capital Cairo witnessed a fourth consecutive day of protests outside the US embassy.
Clashes were reported between protesters and security forces in which one person is said to have died. As the roads leading to the US embassy were closed, the demonstrators are taking other routes.
Hundreds of protesters stormed the historic Tahrir Square hurling stones and petrol bombs at the police. According to official figures, more than 250 people have been injured since the protests started.
"The clashes will continue until President Mursi takes a strong position. ... They aren't for something specific, we are trying to be at the embassy to tell the whole world we are here," an angry protester Ahmed Abdel Gawad told Reuters.
Nearly a half dozen people have died in protests in Khartoum and Tunis.
The US called the Sudanese envoy to Washington and expressed concern over the situation. "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," said the White House.
Thousands of people stormed the US embassy in Khartoum. German and British embassies were also not spared although none of them had any connection with the film.
In Tunisia, two people died during an armed confrontation with police forces. Mild protests were reported in Lebanon, Israel, and Yemen.