TEHRAN (Tasnim) - At least 717 pilgrims were killed Thursday in a stampede outside the Muslim holy city of Mecca, Saudi authorities said, the worst disaster to strike the annual Hajj pilgrimage in 25 years.

At least 805 others were injured in the crush at Mina, a few kilometers east of Mecca, caused by two large groups of pilgrims arriving together at a crossroads on their way to performing the �stoning the devil� ritual at Jamarat, Saudi civil defense said.

Crown Prince Mohammed bin Naif, deputy premier and minister of interior, has ordered a high-level investigation into the incident. He said the findings of the investigation will be submitted to Custodian of the Two Holy Mosques King Salman, �who will take appropriate measures� in response.

Thursday�s disaster was the worst to befall the pilgrimage since July 1990, when 1,426 pilgrims were crushed to death in a tunnel near Mecca. Both stampedes occurred on Eid al-Adha (Feast of the Sacrifice), Islam�s most important feast and the day of the stoning ritual.

Photographs published on the Twitter feed of the Saudi civil defense Thursday showed pilgrims lying on stretchers while emergency workers in high-visibility jackets lifted them into an ambulance.

The Hajj, the world�s largest annual gathering of people, has been the scene of numerous deadly stampedes, fires and riots in the past, but their frequency was greatly reduced in recent years as the government spent billions of dollars upgrading and expanding Hajj infrastructure and crowd control technology.

Safety during Hajj is a politically sensitive issue for the kingdom�s ruling Al Saud dynasty, which presents itself internationally as the custodian of its holiest places in Mecca and Medina.

Unverified video posted on Twitter showed bodies, clad in the white toweling of those undertaking Hajj, lying on the ground by the side of the road, surrounded by debris, as pilgrims and rescue workers attempted to revive them.

By Tasnim News Agency