More than a million Muslims are gathering in Mecca for the hajj pilgrimage overshadowed by the Middle East war, as animosity smoulders across the region despite a fragile ceasefire.

This year's rites, drawing worshippers from across the Islamic world including Iran, follow waves of Iranian attacks on targets in Saudi Arabia and its Gulf neighbours.

Saudi officials are keen to keep conflict far from the minds of visitors, who have travelled long distances for one of the world's biggest annual pilgrimages.

But for Fatima, a 36-year-old German housewife travelling with her family, "there was no second thought" about coming to Mecca, Islam's holiest city.

"We know we are at the safest place in the world," she told AFP.

The hajj, one of the five pillars of Islam, must be performed at least once by all Muslims with the means.

As of this week, more than 1.2 million pilgrims had arrived in Saudi Arabia for the multi-day pilgrimage starting Monday, officials said.

No flags, no chanting

The hajj has been a point of tension in the past between Riyadh and Tehran, with repeated outbreaks of violence and unrest involving Iranian visitors.

In the years following Iran's 1979 Islamic revolution, Saudi authorities accused Iranian pilgrims of triggering stampedes and other violence, while also chanting political slogans -- an act seen as taboo by the religious establishment in Mecca.

A Saudi state broadcaster this week posted a warning from the interior ministry saying any chanting or raising political or sectarian flags were strictly prohibited during the hajj.

The last major dispute erupted in 2015, when 464 Iranians were among 2,300 pilgrims killed in a stampede -- one of the hajj's biggest tragedies -- prompting accusations between Riyadh and Tehran.

Relations were severed a year later after protesters attacked Saudi Arabia's embassy in Tehran and consulate in the northwestern city of Mashhad, following Riyadh's execution of Shiite cleric Nimr al-Nimr.

No Iranian pilgrims were allowed that year, as the two sides were unable to organise a protocol for them to attend.

Experts, however, said authorities would do their utmost to prevent any unrest from rattling this year's pilgrimage.

"Saudi Arabia and Iran have kept their political engagement open" despite the war, said Umer Karim, an expert on Saudi foreign policy.

Blazing sun

The two sides only re-established relations in a surprise 2023 deal brokered by China, which saw tensions ease and embassies reopen in their respective capitals.

But the detente was upended following the US and Israeli attack on Iran in late February that set off Iran's wide-ranging retaliation against its Gulf neighbours.

Energy installations, airports, export terminals, ports and other civilian infrastructure were targeted by Tehran, as Iranian attacks on the Strait of Hormuz choked Gulf oil and gas exports to the outside world.

Despite the fighting, Iranian pilgrims began arriving in the kingdom in late April, with tens of thousands estimated to take part in the hajj.

As well as geopolitical tensions, the arduous, outdoor pilgrimage will again be held under punishing sun, with temperatures forecast to top 40 degrees Celsius (104 degrees Fahrenheit) for much of the week.

After more than 1,300 people died in 2024, when temperatures soared above 50 degrees Celsius, Saudi authorities introduced a range of heat-mitigation measures including more shaded areas and thousands of extra health workers.

More than 50,000 healthcare staff and 3,000 ambulances are on hand to help pilgrims in need, the Saudi health ministry said.

Despite the heat and war, pilgrims were overcome with emotion as they kickstarted the hajj festivities in Mecca, Islam's holiest city.

"Hajj has been the dream of a lifetime for me," Ahmed Abo Seta, 47, told AFP. "And it is finally coming true."