The US State Department has ordered the withdrawal of all non-essential diplomatic staff and their families from Tunisia and Sudan.

Embassies in both countries have been attacked in recent days, during protests over an anti-Islam film produced in the US.

In a statement the State Department said it “urges U.S. citizens to avoid all travel to the Darfur region of Sudan, the Blue Nile and Southern Kordofan States,” and that it advises citizens to “consider carefully the risks of travel in other areas of Sudan.”

The Sudanese government earlier refused permission for the arrival of US marines to help protect the embassy, saying that Sudanese forces are capable of protecting the compound.

The State Department also released a statement on Tunisia, saying that it had ordered all non-essential staff to leave Tunisia and that "US citizens remaining in Tunisia should use extreme caution and avoid demonstrations,"

Protests against US embassies have spread as far as Sydney, where police had to hold protestors back from entering the consulate compound.

News agency AP reported Grand Mufti Sheik Abdel-Aziz al-Sheik, the highest religious authority in Saudi Arabia, as saying that Muslims should "denounce it without anger".

"Muslims should not be dragged by wrath and anger to shift from legitimate to forbidden action and by this, they will, unknowingly, fulfil some aims of the film."