Police used tear gas to disperse the protesters after they threw stones and petrol bombs near the embassy, state television reported.

The demonstrators set a police van on fire and blocked a road leading to the embassy near Tahrir Square in central Cairo, according to the report.

Protesters had scaled the walls of the fortified embassy building on Tuesday and replaced the US flag with a black banner popular with radical Islamists.

The demonstrators are demanding an official US apology over the video, which has sparked outrage in other Muslim countries.

US President Barack Obama called on the leaders of Libya and Egypt to ensure the safety of US diplomatic facilities and personnel, the White House said Thursday, after four Americans were killed in an attack on the US consulate in Benghazi.

Obama "underscored the importance of Egypt following through on its commitment to cooperate with the United States in securing US diplomatic facilities and personnel," the White House statement said.

Meanwhile, Egypt's chief prosecutor, Abdul-Maguid Mahmoud, has placed US pastor Terry Jones and 10 Coptic Christians staying in the United States on a watch list at the country's border checkpoints in connection with their reported involvement in producing the "blasphemous" video, state media reported Thursday.

Jones, the obscure leader of a little-known church in Florida, has periodically provoked outrage in the Muslim world by burning or threatening to burn the Koran.

On Tuesday, the anniversary of the September 11, 2001, attacks on the US, Jones praised the video, Innocence of Muslims, which he said showed "the destructive ideology of Islam."