Hundreds of thousands of Muslim pilgrims crowded Saudi Arabia's Mount Arafat on Tuesday, the climax of a potentially record-breaking hajj pilgrimage held in fierce summer heat.

As dawn broke, groups of worshippers recited Koran verses on the rocky rise, where the Prophet Mohammed is believed to have given his final sermon.

The ritual is the high point of the annual pilgrimage, one of the five pillars of Islam, that officials say could be the biggest on record after three years of Covid restrictions.

More than 2.5 million pilgrims were expected to join the hajj, one of the world's largest religious gatherings and a source of legitimacy for the oil-rich country's royal rulers.

Temperatures soared to 46 degrees celsius (113 Fahrenheit) on Monday as robed worshippers shielded by umbrellas journeyed from Mecca to Mina, where they slept in a giant tented city before the rites at Mount Arafat.

Egyptian schoolteacher Tasneem Gamal said she was emotionally overwhelmed to arrive at Arafat, whose rituals are a compulsory part of the pilgrimage. 

"I cannot describe my feelings, I am living a great joy," the 35-year-old woman said.

Gamal is performing the hajj without a male guardian, a requirement that was shelved by Saudi authorities until 2021.

This year, a maximum age limit has also been removed, giving thousands of elderly the chance to attend.

Tuesday provides the biggest physical challenge, as pilgrims will spend hours praying and reciting the Koran on Mount Arafat and in the surrounding area amid high temperatures.

Unlike Mecca, dotted with hotels and malls, and the tents of Mina, air-conditioned shelter is scarce.

- 'Blessed' -

As helicopters buzzed overhead, entry roads were packed with worshippers. Thousands of health workers were on alert for cases of heat stroke and exhaustion. 

The heat risk will be highest from 12:00 pm to 3:00 pm, when outdoor labour is banned in Saudi Arabia between June and September to protect workers.

After sunset, pilgrims will travel the short distance to Muzdalifah, halfway between Arafat and Mina, to sleep in the open air.

The following day, they will gather pebbles and hurl them at three giant concrete walls in the symbolic "stoning of the devil" ritual.

The last stop is back at Mecca's Grand Mosque, where they will perform a final circumambulation of the Kaaba, the giant black cube that Muslims worldwide pray towards each day.

Heat is not the only risk at hajj, which has seen multiple crises over the years, including militant attacks and deadly fires.

In 2015, a stampede killed up to 2,300 people. There have been no major incidents since.

Before heading to Arafat, American engineer Ahmed Ahmadine said he felt "blessed" to be able to take part in the pilgrimage.

"I try to focus on praying for my family and friends, " said the 37-year-old. 

"This is an opportunity that will not be repeated."

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