At least 717 people were killed and hundreds more injured in a stampede on the outskirts of Mecca on Thursday - the deadliest tragedy to strike the annual hajj pilgrimage in more than two decades.

It was the second major disaster during this year's hajj season, raising questions about the adequacy of the safety measures put in place by Saudi authorities.

A crane collapse in Mecca nearly two weeks ago left more than 100 people dead.