Men don a seamless shroud-like white garment that emphasises unity among believers, regardless of their social status or nationality.
Women, in turn, wear loose dresses exposing just their faces and hands.
Authorities said over 1.5 million pilgrims had arrived in Saudi Arabia for the hajj, one of the five pillars of Islam that must be performed at least once by all Muslims with the means.
Officials have ratcheted up heat protection measures such as extra shade to avoid a repeat of last year, when 1301 people died as temperatures hit 51.8C.
“Last year, the heat was extremely intense, and people were lying on the streets, on the middle of the road and next to the walls,” Alaa Refai, a pilgrim from Iraq, told AFP, adding that he saw several dead people during the previous hajj.
“This year the roads are empty,” he added.
Artificial intelligence
Following last year’s lethal heatwave, authorities have mobilised more than 40 government agencies and 250,000 officials to improve protection.
Shaded areas have been enlarged by 50,000sq m, thousands of additional medics will be on standby and more than 400 cooling units will be deployed, Hajj Minister Tawfiq al-Rabiah told AFP last week.
Artificial intelligence technology will help process the deluge of data, including video from a new fleet of drones, to better manage the massive crowds.
“The scene in Mina this year was completely different. We noticed that most pilgrims kept to their... tents instead of exposing themselves to the sun,” Ibrahim bin Saleh Al-Mazni, from the Al-Furqan group for hajj tours, told AFP from Mina.
“This reflects the success of the awareness campaign” of authorities, he added, which have been striving to dissuade pilgrims from staying in the sun – with many faithful believing hardship was essential to hajj.
Earlier this week, Saudi authorities called on pilgrims to stay inside their tents between 10am and 4pm on Thursday during the hajj’s climax at Mt Arafat, when the desert sun is at its harshest.
There, pilgrims assemble on the high hill and its surrounding plain for hours of prayer and Koran recitation, staying there until the evening.
There is little to no shade on Mt Arafat, leaving pilgrims directly exposed to the blistering desert sun for hours.
‘No hajj without permit’
Authorities said most of the deaths last year were among unregistered pilgrims who lacked access to air-conditioned tents and buses.
This year, they have cracked down on the unregistered, using frequent raids, drone surveillance and a barrage of text alerts.
A billboard reading “No hajj without permit” greeted pilgrims as they arrived in Mecca.
Hajj permits are allocated to countries on a quota basis and distributed to individuals by lottery.
But even for those who can obtain them, the steep costs prompt many to attempt the hajj without a permit, even though they risk arrest and deportation if caught.
Large crowds at the hajj have proved hazardous in the past, most notably in 2015 when a stampede during the “stoning the devil” ritual in Mina killed up to 2300 people in the deadliest hajj disaster.
Saudi Arabia earns billions of dollars a year from the hajj, and the lesser pilgrimage known as umrah, undertaken at other times of the year.
-Agence France-Presse