An aerial view shows the Clock Tower and the Grand Mosque in Makkah, on Friday.

Reuters/Mina

Saudi Arabia on Friday suggested pilgrims ignoring crowd control rules bore some blame for a crush that killed over 700 people at the Haj pilgrimage in the annual event's worst disaster for 25 years.

Iran expressed outrage at the deaths of 131 of its nationals at the world's largest annual gathering of people.

With pilgrims frantically searching for missing compatriots and photographs of piles of the dead circulating on social media, the tragedy haunted many on the Haj a day later.

"There were layers of bodies, maybe three layers," said one witness who asked not to be named. "Some people were alive under the pile of bodies and were trying to climb up but in vain, because their strength failed and they dropped dead."

"I felt helpless not to be able to save people. I saw them dying in front of my eyes."

Saudi Health Minister Khalid al-Falih said an investigation would be conducted rapidly and a final toll of dead and wounded calculated. At least 863 pilgrims were injured.

The stampede "was perhaps because some pilgrims moved without following instructions by the relevant authorities," he said in a statement.

A pilgrim who gave his name as Abu Abdallah said security forces appeared on high alert after the deaths. "What happened is a tragedy and many people ... are terrified, but in the end we can only pursue our Haj duties," he said.

Hakim, from Morocco, said: "It is simply scary to hear how people crushed one another. More frightening is that we do not know how it happened."

Saudi King Salman ordered a review of Haj plans after the disaster, in which two big groups of pilgrims collided at a crossroads in Mina, a few km east of Makkah, on their way to performing the "Stoning of the Devil" ritual at Jamarat.

Iran's President Hassan Rouhani, in New York to attend the UN General Assembly, echoed Supreme Leader Ayatollah Ali Khamenei in blaming Saudi Arabia for the incident.

"I ask the Saudi Arabian government to take responsibility for this catastrophe and fulfil its legal and Islamic duties in this regard," Rouhani said in a statement.

Saudi Arabia's Interior Ministry spokesman Major General Mansour Turki was quoted in Saudi media on Friday as saying the security forces had immediately responded and begun to rescue those who fell in the crush.

Speaking in New York, Pope Francis expressed "my sentiments of closeness" with Muslims after the tragedy. UN Secretary General Ban Ki-moon and the US offered condolences.

Foreign toll in Haj stampede

Saudi authorities have yet to provide a breakdown of the nationalities of the 717 pilgrims killed in Thursday's stampede, but several foreign countries have announced the deaths of nationals.

Here is the toll given by foreign officials and media so far:

Algeria: 3 dead

Burundi: 1 dead

Cameroon: about 20

Chad: 11

Egypt: 14 dead

India: 14 dead

Indonesia: 3 dead

Iran: 131 dead

Kenya: 3 dead

Morocco: 87 dead, according to Moroccan media

Netherlands: 1 dead

Pakistan: 7 dead

Senegal: 5 dead

Somalia: 8 dead, according to media reports

Tanzania: 4 dead