Muslim pilgrims are gathering in the Saudi city of Mecca for Islam's annual pilgrimage, which begins Wednesday.
Able Muslims are required to perform the arduous and expensive pilgrimage to Mecca, known as the Hajj, at least once in their lifetime.
Saudi authorities are warning they will stop any disruptive protests over the conflict in Syria.
Saudi Arabia has backed rebels fighting Syrian President Bashar al-Assad, while Iran remains an ally of Syria at a time when relations between Riyadh and Tehran are tense.
Authorities say they are prepared for possible violence during the pilgrimage, which has happened in the past. The most notable case came in 1979, when attackers seized the Grand Mosque. Hundreds of people were killed during a two-week siege.