The world's largest annual pilgrimage, the Haj, began today with hundreds of thousands of Muslims pouring into the camp of Mina from Mecca to prepare for solemn rituals.
The pilgrims are estimated to total up to 2.5 million this year, a major headache for the Saudi authorities who have yet to report any major incidents since the faithful descended on the holy city.
Many took buses but some had already set off on foot overnight as they headed to the vast plain of Mina, a small village about five kilometres east of Mecca that comes to life for just five days a year.
Authorities say permits have been granted to 1.7 million foreign pilgrims, with a further 200,000 or so issued to pilgrims from within Saudi Arabia and from neighbouring Gulf states.
This year has seen a crackdown on pilgrims who do not have the requisite papers as authorities attempt to prevent numbers getting out of hand.
A driver caught transporting unauthorised pilgrims faces a fine of 10,000 riyals (US$2,667) for each individual. Vehicles with a capacity below 25 passengers have also been banned from entering Haj sites to streamline the flow of buses transporting pilgrims.
The passage to Mina marks the official launch of the Haj on the eighth day of the Muslim calendar month of Dhul Hijja.
The day is known as Tarwiah (Watering) as pilgrims in the past stopped at Mina to water their animals and stock up for the following day's trip to Mount Arafat.
At Mount Arafat, some 10km southeast of Mina, the pilgrims spend the day in prayer and reflection.
After sunset, they move on to Muzdalifah, halfway between Mount Arafat and Mina, where they spend the night.
On Tuesday, the first day of Eid al Adha or the Feast of the Sacrifice, the pilgrims head back to Mina after dawn prayers.
They then perform the first stage of the symbolic "stoning of the devil" and make the ritual sacrifice of an animal, usually a lamb.
During the remaining three days of the Haj, the pilgrims continue the ritual stoning before performing the circumambulation of the Kaaba shrine in Mecca and heading home.
No major incidents have been reported this year since the pilgrims began gathering in Mecca. The city's Grand Mosque has been flooded with the faithful, with an estimated 1.7 million taking part in the main weekly Muslim prayers on Friday.
The movement of pilgrims between the holy sites is a major worry for Saudi authorities who have had to deal with deadly stampedes in the past.
In recent years, the kingdom has used its huge oil revenues for massive spending on new infrastructure to ease the flow of people.
This year, the first phase of the new Mashair Railway - or Mecca metro - will transport pilgrims between Mina and Mount Arafat through Muzdalifah.
The Jamarat Bridge, where pilgrims perform the ritual stoning, has also been expanded to five levels with movement channelled in one direction.
Security remains a concern. Last Wednesday, Saudi Interior Minister Prince Nayef bin Abdul Aziz said he could not rule out the possibility of a sabotage attempt by al Qa'eda.
Saudi King Abdullah yesterday appointed Prince Nayef, his second deputy prime minister, to replace him in overseeing the Haj as he is resting due to a herniated disc.