Police vehicles drive past pilgrims on a road in Mina, near the holy city of Mecca September 24, 2015.[Photo/Agencies]

BLAME

Iran's Supreme Leader, Ayatollah Ali Khamenei, said the Saudi government should accept responsibility for the crush, in which more than 100 Iranian nationals were reported to have died.

"The Saudi government should accept the responsibility of this sorrowful incident ... Mismanagement and improper actions have caused this catastrophe," Khamenei said in a statement published on his website.

King Salman offered deep condolences.

"We have instructed concerned authorities to review the operations plan ... (and) to raise the level of organisation and management to ensure that the guests of God perform their rituals in comfort and ease," the monarch said.

The Interior Ministry spokesman, Mansour Turki said the investigation would look into what caused an unusual mass of pilgrims to congregate at the location of the disaster. "The reason for that is not known yet," he told a news conference in Mina.