About 100 supporters of the Islamic People's Forum unfurled banners saying "Expel America" and "Death to the filmmaker" in Medan city against the low-budget American film that has sparked furious protests across the Muslim world.

"Under Islamic law the filmmaker who insulted the Prophet Mohammed must be punished by death," one of the protesters told the crowd outside the US mission in the city in North Sumatra province.

"We urge the Indonesian government to expel US diplomats and their allies from this country. These infidels are the real enemies of Islam," the speaker shouted, as some in the crowd trampled on the US flag before setting it on fire.

On Monday, protesters hurled petrol bombs outside the US Embassy in Jakarta in the first violent demonstration over the film, after hundreds protested on Friday and Saturday in largely peaceful demonstrations.

Authorities said 11 policemen and a protester were injured in Monday's clashes, in which police used water cannon and tear gas to control some 700 demonstrators, mostly from hardline Islamic groups.

"Innocence of Muslims", believed to have been produced by a small group of extremist Christian Americans, has triggered a week of furious protests outside US embassies and other American symbols in at least 20 countries.

The movie mocks the Prophet Mohammed and portrays Muslims as immoral and gratuitously violent.

On Tuesday, Australia issued a safety warning to its citizens in Indonesia, saying "further protests at US diplomatic and consular premises are possible".