Enormous crowds of worshippers thronged Mecca, Islam's holiest city, on Friday for the biggest hajj pilgrimage in years,

This year's hajj -- one of the world's biggest annual religious gatherings, with a tragic history of stampedes and other disasters

This year's hajj -

"As the hajj draws near, the Kingdom of Saudi Arabia prepares... for the largest Islamic gathering in history,"

More than two million people from more than 160 countries will attend, Rabiah said -- a dramatic increase on the 926,000 from last year,

The hajj is among the five pillars of Islam and must be undertaken by all Muslims with the means at least once in their lives.

The pilgrimage "gives the kingdom and its rulers a huge amount of esteem and prestige which then becomes a major source of the kingdom's soft power".