717 people die in stampede at Mecca
Another 863 people were injured in the incident at Mina, which occurred as two million pilgrims were taking part in the Hajj's last major rite.
It is the deadliest incident to occur during the pilgrimage in 25 years.
The king said there was a need "to improve the level of organisation and management of movement" of pilgrims.
It is the second disaster to strike Mecca in two weeks, after a crane collapsed at the Grand Mosque, killing 109 people.