More than 1.5 million Muslims braved extreme heat to reach Mount Arafat on Saturday for the high point of the annual hajj pilgrimage, praying for hours, especially for Palestinians in war-ravaged Gaza.

Clad in white, worshippers began arriving at dawn for the most gruelling day of the annual rites, ascending the rocky, 70-meter (230-foot) hill where the Prophet Mohammed is believed to have given his last sermon.

"This is the most important day," said 46-year-old Egyptian Mohammed Asser, who came prepared with a list of prayers. "I pray also for the Palestinians. May God help them." 

This year's hajj is unfolding in the shadow of the war in Gaza between Israel and Hamas, which was triggered by the Palestinian militants' unprecedented attack on southern Israel on 7 October.

The assault resulted in the deaths of 1,194 people, mostly civilians, according to an AFP tally based on Israeli official figures.

Israel's retaliatory military offensive has killed at least 37,266 people in Gaza, also mostly civilians, according to the Hamas-ruled territory's health ministry.

Saudi Arabia's minister in charge of religious pilgrimages, Tawfiq al-Rabiah, warned last week that "no political activity" would be tolerated during the hajj.

But that did not stop at least one pilgrim from chanting in support of the Palestinians who have endured more than eight months of incessant bombardment.

"Pray for our brothers in Palestine, in Gaza... may God give victory to the Muslims," he shouted.

In a message to hajj pilgrims on Saturday, Iranian supreme leader Ayatollah Ali Khamenei said "the ironclad resistance of Palestine and the patient, oppressed people of Gaza... must be fully supported in every way".

Some 2,000 Palestinians are performing the hajj at the special invitation of Saudi King Salman, official media said.

'Scary' heat

The hajj, one of the world's biggest religious gatherings, is increasingly affected by climate change, according to a Saudi study published last month that said regional temperatures were rising 0.4 degrees Celsius each decade.

The rituals, which take at least five days to complete and are mostly outdoors, are "not easy because it is very hot", said Abraman Hawa, 26, from Ghana.

"We have sun... but it is not as hot. But I will pray to Allah at Arafat, because I need his support," she added.

The temperature was expected to hit 43 degrees Celsius (109.4 degrees Fahrenheit) on Saturday, creating challenges for pilgrims who arrived at Mount Arafat after spending the night in a giant tented city in Mina, a valley outside Mecca, Islam's holiest city.

Saudi authorities have urged pilgrims to drink plenty of water and protect themselves from the sun. Since men are prohibited from wearing hats, many carry umbrellas.

More than 10,000 heat-related illnesses were recorded last year, 10 percent of them heat stroke, a Saudi official told AFP this week.

Ahmad Karim Abdelsalam, a 33-year-old pilgrim from India, admitted that he found the prospect of passing hours on Mount Arafat "a little scary".

But with the help of an umbrella and water sprays, "God willing, everything will go well", he said.

'Once in a lifetime'

The hajj is one of the five pillars of Islam and all Muslims with the means must perform it at least once.

Yet visas, doled out to individual countries on a quota system, can be difficult to obtain.

"It's a chance that only comes once in a lifetime, I couldn't not come," said Abdulrahman Siyam, a 55-year-old Iraqi pilgrim who was performing the rituals on a prosthetic leg.

After Mount Arafat, the pilgrims will head to Muzdalifah, where they will collect pebbles to carry out the symbolic "stoning of the devil" ritual in Mina on Sunday.

The hajj is said to follow the path of the Prophet Mohammed's final pilgrimage, about 1,400 years ago.

It is an important source of legitimacy for the Al Saud dynasty, whose monarch has the title "Custodian of the Two Holy Mosques", in Mecca and Medina.

It is also a major financial windfall for the conservative country, which is trying to develop religious tourism as part of a drive to reduce its dependence on crude oil.

The kingdom received more than 1.8 million pilgrims last year for the hajj, around 90 percent of whom came from abroad.

It also welcomed 13.5 million Muslims who came to perform umrah, the pilgrimage which can be done year-round, and aims to reach 30 million pilgrims in total by 2030.