Saudi officials say 717 people have been killed and 805 others injured in a stampede during the hajj, the deadliest tragedy to strike the annual Muslim pilgrimage in 25 years.
Video and photographs published on social media showed pilgrims lying on stretchers while medical workers were trying to resuscitate them at the site in Mina, which is just a few kilometers from Mecca. Injured pilgrims were reportedly transferred to a hospital in Mina.
Some images showed piles of bodies.
Saudi King Salman and Crown Prince and Interior Minister Prince Mohammed bin Nayef bin Abdelaziz ordered an investigation into the deadly incident. Salman also said that he had ordered a review of the kingdom's plans for the annual hajj pilgrimage after the stampede.
Iran blamed Saudi authorities for the tragedy, which took place during the last major rite of the hajj, when hundreds of thousands of people ritually stone the devil by hurling pebbles at three large pillars.
Iran's supreme leader, Ayatollah Ali Khamenei, said the Saudi Arabian government should accept its “heavy responsibility” for the incident that according to Iranian media left more than 100 Iranian pilgrims dead.
“Mismanagement and improper actions have caused this catastrophe," Khamenei said in a statement published by Iranian state news agencies.
Offering condolences to the families of the dead pilgrims, Khamenei declared three days of national mourning in the country.
Said Ohadi, the head of Iran's hajj organization, said on Iranian television that two paths had been closed in Mina and that the closures "caused this tragic accident." He added that the closures had left only three routes to the area where the symbolic stoning takes place.
He said Saudi officials must be "held accountable" for the deaths, which reportedly included Iranian citizens. Officially Sunni Saudi Arabia and officially Shi'ite Iran are regional rivals with tense relations, including over their backing of opposing sides in the Syria and Yemen conflicts. Iran's official news agency IRNA reported that 90 Iranians are among the dead in the stampede.
Iranian Deputy Foreign Minister Hossein Amir Abdollahian also blamed Saudia Arabia for the incident and said that Saudi officials should take immediate steps “to manage the crisis and provide full security for pilgrims.”
Saudi Arabia's health minister blamed pilgrims themselves for the tragedy, saying that failure to follow instructions was "the principal reason for this type of accident." The minister, Khaled al-Falih, was quoted by Saudi media as saying that "many pilgrims move without respecting the timetables" established by authorities to avoid overcrowding.
Interior ministry spokesman General Mansur al-Turki said the stampede was caused when "a large number of pilgrims were in motion at the same time.”
The stoning has traditionally been the most dangerous event of the hajj because vast numbers of pilgrims attempt to perform the ritual at the same time in a single location. The symbolic stoning, known as Jamarat, takes place in a multilevel structure near to the camp city at Mina, where some 160,000 tents house pilgrims at night.
The tragedy occurred as the world's 1.5 billion Muslims marked Eid al-Adha, or the Feast of the Sacrifice, when Muslims traditionally slaughter a sheep for the most important holiday of the Islamic calendar.
The pilgrimage, the world's largest annual gathering of people, has been the scene of deadly stampedes in the past as well as other disasters including tent fires and riots.
In 1990, at least 1,426 pilgrims were killed in a stampede in a tunnel in Mina after a failure in its ventilation system.
In January 2006, 364 pilgrims were killed in a stampede during the stoning ritual in Mina.
However, such events have become less common in recent years as the Saudi government has invested heavily in infrastructure improvements and crowd control technology.
The stampede on September 24 is the second major tragedy in Saudi Arabia this month. On September 11, 111 people were killed when a crane collapsed at Mecca's Grand Mosque, Islam's holiest site.
There are at least 2 million Muslims from 164 countries in Saudi Arabia performing the five-day hajj, which began on September 22.
The hajj is among the five pillars of Islam and all Muslims must perform it at least once in a lifetime if they have the means to do so.
The United States offered its condolences over the deaths in the “heartbreaking” stampede in Mina.
National Security Council spokesman Ned Price said "as Muslims around the world continue to celebrate Eid al-Adha, we join you in mourning the tragic loss of these faithful pilgrims."