Jerusalem police clashed with hundreds of Muslim youth Friday after they left prayers atop the Temple Mount in the direction of the Damascus Gate. Police said the rioters were on their way to the US consulate, presumably to protest against a film denigrating the Prophet Mohammad, which has already sparked mass protests in Libya, Egypt and Yemen.

The youths threw stones at the police officers, who responded by firing stun grenades to disperse the protest. A number of officers were lightly injured from smoke inhalation. Forces arrested four of the rioters.

Police were prepared for the possibility of riots in Jerusalem, as Border Police and other patrol units fanned out across the Old City ahead of traditional Friday prayers.

Despite an awareness of potential violence, police did not announced restricted access to the Temple Mount. Often if serious rioting is anticipated only men over age 40 are allowed to enter.

In a rare move, the US State Department on Thursday issued a travel warning for Jerusalem, urging American citizens to “defer nonessential travel and exercise caution.”