(Bloomberg) -- Saudi Arabia said more than 1,300 pilgrims died during the annual Hajj pilgrimage, as temperatures during the gathering reached the highest level in two decades.

The majority of fatalities were unregistered pilgrims, who were not authorized to participate and walked long distances without adequate shelter, according to the official Saudi Press Agency. Many of the dead were elderly and chronically ill, it said. 

The fatalities put a fresh spotlight on the threat from a hotter world and the risk it poses for large gatherings. Heat related deaths have been reported in India, wild fires are forcing evacuation of people on Greece, parts of the US are in the middle of a heat wave and there are fears that rising temperatures may increasingly make some parts of the Middle East difficult to live.

In Saudi Arabia, temperatures reached about 52C (126F) during the five-day pilgrimage that ended June 18, the highest level recorded during Hajj for 20 years, according to data from the Saudi National Center for Meteorology. More than 1.8 million worshippers participated in this year’s Hajj.

Saudi authorities had earlier cautioned about “the significant rise in temperatures, which poses a threat to the health of pilgrims.” The health ministry later urged people to use umbrellas to prevent sun exposure. Over 2,700 cases of heat stroke were reported last Monday alone.

The majority of deceased pilgrims came from countries including Egypt, Jordan, Indonesia, India and Pakistan, according to earlier reports from Agence-France Press, which cited diplomats.

Deaths at Hajj aren’t uncommon due to a variety of reasons. A stampede in 2015 killed hundreds of people. Heat stroke caused 1,012 deaths back in 1985 when the pilgrimage was in August and average temperatures reached 54C, according to a report from the Annals of Saudi Medicine.  

This year, the Saudi health ministry said treatment was given to almost half a million people, including 141,000 unauthorized pilgrims. Services included open-heart surgeries, cardiac care and air ambulance operations. Saudi Arabia also said it made almost 6,500 beds and rooms available to those who needed care.

The country’s health minister praised the “successful execution of health management efforts” during the Hajj season, according to the Saudi Press Agency report on Sunday.

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--With assistance from Fahad Abuljadayel.

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