At least 719 Hajj pilgrims were killed on Thursday in a stampede at Mina, five kilometers outside of the Muslim holy city of Mecca, Saudi Arabia's civil defence authority reported on Twitter.
Currently, 4000 rescue workers are reported to be at the scene along with 220 ambulances.
— الدفاع المدني (@KSA_998) September 24, 2015
A state of emergency has been declared in all nearby hospitals.
Precautions were taken before the annual ritual commenced as Saudi Arabia increased security measures and reduced the number of people it will take in from each Muslim country.
It is estimated that close to two million pilgrims will perform the Hajj this year.
Pilgrims stay overnight at Mina during their pilgrimage and carry out a symbolic act of stoning the devil by throwing pebbles against three stone walls.
— Basma Atassi | بسمة (@Basma_) September 24, 2015
Throughout history Mecca has witnessed similar stampedes which have killed hundreds of pilgrims. However, such an incident had not occurred since 2006 after the Saudi government stepped up safety measures. The most severe stampede, which claimed the lives of 1,426 people, occurred in 1990 when pilgrims were crushed inside the tunnel from Mecca to Mina.
Earlier this month at least 107 people lost their lives after a crane collapsed onto Mecca's Grand Mosque. Severe weather conditions appear to have been the main cause of the accident, although Saudi authorities have reported that investigations are still ongoing.
The Hajj is considered to be a religious duty for all Muslims and it is expected that they carry it out at least once in their lifetimes if they are able to do so.