Pilgrims in their hundreds of thousands thronged Mount Arafat in Saudi Arabia from early Monday for the climax of the annual hajj pilgrimage, arriving on foot, by train or in vehicles.
Officials said they expected around 1.5 million pilgrims to descend on the site, where later in the day they will perform prayers and listen to the annual sermon from Saudi top cleric Sheikh Abdulaziz al-Sheikh.
Helicopters hovered overhead and thousands of troops stood guard to organise roads flooded by men, women and children streaming towards Mount Arafat.
The numbers are sharply down from last year, due to fears linked to the MERS virus and to expansion work.
Governor of Mecca province and head of the central hajj committee Prince Khaled al-Faisal said 1.38 million pilgrims had arrived from outside of the kingdom while ony 117,000 hajj permits were issued for domestic pilgrims.
This puts the number of pilgrims this year at almost 1.5 million, less than half of last year's 3.2 million after Riyadh slashed hajj quotas for foreign and domestic pilgrims because of massive construction works at the Grand Mosque in Mecca and fears linked to the MERS virus.
Prince Khaled told the official SPA news agency late Sunday that authorities have turned back 70,000 nationals and expatriates for not carrying legal permits and have arrested 38,000 others for performing the hajj without a permit.
Authorities have also seized as many as 138,000 vehicles for violating the hajj rules and its owners will be penalised, the prince said.
Saudi health authorities reiterated on Sunday that no cases of the Middle East Respiratory Syndrome (MERS) virus had been detected. The disease has killed 60 people worldwide, 51 of them in Saudi Arabia itself.
The pilgrims were arriving Monday from nearby Mina where most of them spent the night following the traditions of Islam's Prophet Mohammed who performed the rituals 14 centuries ago.
They had moved to Mina on Sunday from the holy city of Mecca, home to the Grand Mosque, Islam's holiest place of worship which houses the cube-shaped Kaaba structure towards which all Muslims pray daily five times.
They will crowd onto the hill and the vast plain surrounding it praying until sunset when they then set off for nearby Muzdalifah.
There they will then spend the night before moving on in the morning to start the ritual of symbolically stoning the devil.
The hajj, which officially ends on Friday, is one of the five pillars of Islam that every capable Muslim must perform at least once.