Hundreds of thousands of pilgrims on Friday began the symbolic "Stoning the Devil" ritual as part of the annual Haj pilgrimage in the holy city of Makkah.
Large numbers of security forces have been deployed across the Saudi desert valley of Mina, a tent city located around 7 kilometres north-east of Makkah, to prevent any stampede during the three-day stoning rite.
The ritual was ongoing as Muslims around the world started celebrating Eid al-Adha, Islam's holiest festival.
The pebble-throwing ritual was running smoothly at designated walls inside a multilevel structure known as the Jamarat Bridge in Mina, the official Saudi news agency SPA reported.
The pilgrims, clad in seamless pieces of white cloth, chanted "God is the greatest" each time they cast a pebble. Their snow-white garments symbolise equality, religious unity and pursuit of spiritual renewal.
After finishing the stone-throwing ritual on the first day of Eid al-Adha, male pilgrims traditionally shave or cut their hair and change out of their seamless robes. Women cut a lock of their hair.
Male and female pilgrims then go to Makkah and again walk all the way around the cube-shaped Kaaba, to which Muslims direct in their prayers. 
Later in the day, they return to Mina to stay overnight and throw stones for two more days.
In 2015, hundreds of pilgrims were crushed to death in the ritual, a tragedy that triggered tensions between Saudi Arabia and Iran.
Some 769 pilgrims died in that stampede, according to Saudi official figures.
A DPA tally and other independent reports, however, indicated that around 2,000 pilgrims died in the crush. Iran said more than 460 of its citizens were killed in that disaster.
Around 2.3mn people are attending this year's Haj, according to official Saudi figures.
Iranians are participating in the event, which they boycotted last year due to a row between with Saudis on pilgrimage regulations.
This year's Haj comes amid a diplomatic crisis between a Saudi-led Arab bloc and Qatar over the emirate's alleged support for extremist groups, a charge that it has denied.
Qatar has accused Saudi Arabia of creating obstacles for Qatari pilgrims.
Devout Muslims are expected to perform the Haj, one of Islam's five pillars, at least once in their lifetime, provided they are fit enough and have the financial means to do so.