Viast crowds of pilgrims made solemn circles around the Kaaba, the black cube at Makkah's Grand Mosque, on Sunday as  hajj began, AFP reports.

Islam's holiest site is expected to host more than two million worshippers from 160 countries during the annual rites that could break attendance records, with 1.6 million foreigners already arrived by Friday evening.

The hajj began early on Sunday with the "tawaf" -- the circumambulation of the Kaaba, the large cubic structure draped in black cloth with gold trimmings that millions of Muslims pray towards every day.

"I am living the most beautiful days of my life," said Abdel-Azim, a 65-year-old Egyptian as he performed the ritual.

"The dream has come true," said the retiree, who saved up for 20 years to pay the $6,000 fee to take part.

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

A series of rites are completed over four days in Makkah and its surroundings in the west of Saudi Arabia.

On Sunday night, pilgrims will start moving to Mina, about five kilometres (three miles) from the Grand Mosque, ahead of the hajj's climax at Mount Arafat, where the Prophet Mohammed (PBUH) is believed to have delivered his final sermon.

Outside the Grand Mosque, thousands prayed on colourful carpets that adorned the pavement, with male pilgrims wearing a simple white robe. The area was dotted with ambulances, mobile clinics and fire trucks.