Nearly two million pilgrims visited Arafat on the second and most significant day of the annual Haj pilgrimage, near the holy city of Mecca in Saudi Arabia.
Saudi Arabia has said that 1.85 million pilgrims, a lot of them from outside Saudi Arabia, have arrived for the annual pilgrimage, a religious duty for every able-bodied Muslim who can afford the journey.
Muslims on the five-day pilgrimage spent a day there in deep prayer, many openly weeping as they repented and asked God for forgiveness.
The stoning - expected to continue on Tuesday - coincided with Eid al-Adha, Islam's feast of sacrifice which is celebrated by more than 1.5 billion Muslims worldwide.
Thanks to computer technology and SMS messaging, Muslims at the annual Hajj pilgrimage to Makkah were able on Monday to make their Eidul Azha sacrifice without getting blood on their hands.
After sunset, the throng was on the move aboard buses heading for nearby Muzdalifah, in preparation for the stoning ritual.
In what looked like an unbroken sea of white the pilgrims marched to the top, reciting prayers and supplications.
Sheep are slaughtered and the meat distributed to needy Muslims, symbolizing the prophet Abraham's willingness to sacrifice Ishmael on the orders of God, who provided a lamb in the boy's place at the last moment.
Shammari said, "This led to the severance of diplomatic ties [by Riyadh], and Iran stopped its pilgrims from doing the hajj this year despite the flexibility shown by Saudi officials, but it seems this is serving the agenda of certain lines in Iranian politics".
Saudi Arabia cut ties with Iran last January after demonstrators set fire to the Saudi embassy in Tehran following Riyadh's execution of a prominent Shi'ite cleric, Sheikh Nimr al-Nimr.
Among these is the distribution of a bracelet which stores pilgrims' personal data.
Pilgrims have said they feel safe and have noticed organisational improvements. "I am very happy and I hope everything goes well until the end of hajj", said Saudi pilgrim Bashar Aatabi, 30. The tragedy took place as pilgrims were going to the Jamarat Bridge for a stoning ritual which this year will start on Monday.
On Sunday, police were seen directing foot traffic and using drones to monitor crowd movement.
But that's not enough for Iran, which opted instead to endorse an alternative pilgrimage to Karbala, an Islamic holy site in Iraq.
The Hajj to Islam's holiest sites, housed in western Saudi Arabia, is one of the five pillars of the religion that capable Muslims must perform at least once.
In the days leading to this year's hajj, which began yesterday in western Saudi Arabia, Tehran renewed criticism of the kingdom's handling of the annual rites and of a deadly stampede last year.