At least 550 visitors have died during the annual Muslim pilgrimage to Mecca amid scorching heat.

Three hundred and twenty-three of the dead were Egyptians, most of whom perished owing to heat-related illness, Arab diplomats said.

Stampedes, tent fires and other accidents have caused hundreds of deaths during haj to Saudi Arabia in the past 30 years. The pilgrimage began on Friday.

Saudi state TV said temperatures rose on Monday as high as 125.2F (51.8C) in the shade at the Grand Mosque in Mecca.

A 2024 study by the Journal of Travel and Medicine found that rising global temperatures may outpace strategies to deal with the heat. A 2019 study by Geophysical Research Letters said that as temperatures rise in arid Saudi Arabia because of climate change, pilgrims performing haj will face “extreme danger”.

Thirty-five Tunisian citizens have died during the haj, Tunisian news agency Tunis Afrique Presse said on Tuesday.

Many of those deaths were because of extreme heat, family members said on social media, as other families continued to search for missing relatives in Saudi hospitals.

The Jordanian foreign ministry said it had issued 41 burial permits for Jordanian pilgrims on Tuesday. Earlier, the ministry said at least six Jordanian citizens died of heat stroke during the haj.

Eleven Iranians have died and 24 were hospitalised during the pilgrimage, Iranian state news outlet IRINN said on Tuesday without giving the causes of death.

Three Senegalese citizens also died during haj, Agence de Presse Sénégalaise, said on Monday.

144 Indonesian citizens died during the pilgrimage, Indonesian health ministry data showed on Tuesday. The data did not specify if any of the deaths were from heat stroke.

The haj is an annual pilgrimage that millions of Muslims make to Mecca to perform religious rites as taught by the Prophet Mohammad to his followers 14 centuries ago. More than 1.8 million pilgrims were expected to take part this year, according to the Saudi General Authority for Statistics. Haj, one of the largest mass gatherings in the world, is a once-in-a-lifetime duty for able-bodied Muslims who can afford it. It will end on Wednesday.

A Saudi health official, speaking to Reuters on Monday, before many of the reports of deaths were issued, said that authorities had not noticed any unusual fatalities among Muslim pilgrims amid the extremely high temperatures.

The ministry had so far treated more than 2,700 pilgrims who suffered from heat-related illness, he added.

“Haj is a difficult task, so you have to exert efforts and perform the rituals even in the conditions of heat and crowding,” an Egyptian pilgrim told Reuters on Sunday.

Pilgrims used umbrellas to protect themselves from the sun, as Saudi authorities warned pilgrims to stay hydrated and avoid being outdoors during the hottest hours between 11 am and 3pm local time.