Enormous crowds of worshippers thronged Mecca, Islam's holiest city, on Friday for the biggest Hajj pilgrimage in years, with more than two million expected to brave the scorching Saudi Arabian heat.

Pilgrims in white robes and sandals packed the ancient city, now dotted with luxury hotels and air-conditioned shopping malls, after flooding in on planes, buses and trains for the annual rites.

This year's Hajj — one of the world's biggest annual religious gatherings, with a tragic history of stampedes and other disasters — could break attendance records, officials said.

'As the Hajj draws near, the Kingdom of Saudi Arabia prepares- for the largest Islamic gathering in history,' Minister of Hajj and Umrah Tawfiq Al Rabiah said in a video published by the ministry this week.

Rites include circling the Kaaba, the large black cube in Mecca's Grand Mosque, praying on Mount Arafat and 'stoning the devil' by throwing pebbles at three giant concrete walls representing Satan.

More than two million people from more than 160 countries will attend, Rabiah said — a dramatic increase on the 926,000 from last year, when numbers were capped at one million post-pandemic.

In 2019, about 2.5 million people took part.

Only 10,000 were allowed in 2020, at the height of the Covid-19 pandemic, rising to nearly 59,000 a year later.

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.