As the pilgrimage rituals began Tuesday, Saudi authorities took elaborate precautions, deploying 50,000 security forces to prevent the catastrophes of past years when hundreds have been killed in fires and stampedes.

''I feel so enlightened and so much closer to Allah that I can barely wait to stand on the mountain of mercy,'' said Afzal Sikandar Khan, 45, a pilgrim from India, referring to Mount Arafat, the place where, according to Islamic tradition, the Prophet Muhammad delivered his last sermon.

Two million people travel to Islam's holiest sites in Saudi Arabia each year to participate in the hajj, which serves to wipe away accumulated sins.

The pilgrimage is required of able-bodied Muslims at least once in a lifetime, if they can afford it. Pilgrims travel to the sites of Mecca, Mina, Arafat and Muzdalifa.

The pilgrims begin the rituals by first circling the Kaaba, a large black stone structure in Mecca that Muslims face during their five daily prayers.

They then spend a night in the tent city of Mina, and head the next day to pray at Mount Arafat, the central rite of the pilgrimage.

More than a million sheep have been imported for slaughter the day after the hajj to mark the beginning of Eid al-Adha, or the Feast of the Sacrifice.

Many pilgrims remain concerned about hazards such as stampedes and fires.

''I will pray for the tsunami victims, but my immediate concern is that Allah enables us to complete our pilgrimage safe and sound,'' said Nigerian doctor Mokhtar Ahmed, 30.

The tent city in Mina bears many reminders of a 1997 fire that killed more than 340 people. More than 40,000 white fireproof tents are being used, and dozens of fire engines are on standby.

Saudi authorities have expressed concerns about terrorism and the spread of diseases. The kingdom has mobilized counterterror squads and set up medical centers to treat sick pilgrims.