Saudi Arabian authorities have tightened security for the annual Hajj pilgrimage to Mecca, partly because of concerns about demonstrations against a possible U-S-led war in Iraq.
About two million Muslims are expected to participate in this year's Hajj, which gets underway Saturday.
Saudi officials say any attempt to disrupt the pilgrimage will be dealt with by an iron fist. Special forces equipped with water cannons joined troops and police in a show of force Friday.
Muslims converge every year on Mecca and Medina - the two holiest sites of Islam - to take part in the five-day pilgrimage.
All Muslims are required to make the pilgrimage to Mecca at least once in their lifetime, provided they have the means to do so.
Saudi Arabia's Interior Minister (Prince Nayef) says security forces are in a state of highest readiness, and he warned that his country will not allow anyone to threaten its security.
In 1987, Saudi security forces clashed with Iranian pilgrims who staged an anti-U-S rally in Mecca. Hundreds of pilgrims were killed in those clashes.