Some two million Muslims from across the world have converged on the holy city of Mecca amid razer-sharp Saudi security to perform the hajj pilgrimage which begins Tuesday.

For weeks pilgrims have been flooding into the birthplace of Prophet Mohammed to take part in the annual rituals, which will climax Wednesday on Mount Arafat where the prophet gave his last sermon 14 centuries ago.

Battling a wave of al-Qaeda-linked attacks since May 2003, Saudi authorities have mobilised more than 50,000 security men in Mecca to ensure that violence does not mar the sanctity of the life-defining hajj.

Security forces will have to work round-the-clock to ensure the masses pass smoothly through the rites to avoid a repetition of tragedies in recent years in which hundreds have been crushed to death in stampedes or fires.

Last year, 251 pilgrims were trampled or suffocated to death during a crush as they vied to stone three pillars representing the devil in Mina, near Mecca.

This year, pilgrims are due to travel to Mina on Tuesday evening where they will spend the night under canvas before catching the bus or walking to Mount Arafat for a ritual which symbolises the Last Judgement.

They will return to Mecca on Thursday, the first day of Eid al-Adha, or Feast of the Sacrifice, when most of them will sacrifice an animal, generally a sheep, in remembrance of Abraham’s readiness to sacrifice his son to God.

To cater for demand, Saudi shopkeepers have imported more than a million sheep, largely from Sudan and Uruguay, according to Sayed Abdelrahman, a veterinary officer at the nearby Red Sea port of Jeddah.

On Friday and Saturday, the pilgrims will return to Mina to stone the three statues representing Satan, the ultimate rite of pilgrimage.

Waiting for the rites to begin, pilgrims have spent most of their time praying in Mecca’s Grand Mosque, the holiest in Islam, or walking around the Kaaba, the cube-shaped structure revered by Muslims as the house of God.