More than 1,000 people have now died during the Hajj pilgrimage to the city of Mecca, it has been reported.
That is a rise of almost 500 on yesterday, according to figures from the AP news agency.
Temperatures have reached at least 51.8C (125F) in the shade in the Saudi Arabian city – the holiest city in Islam.
The new figure includes another 58 Egyptians, bringing to 658 the number of Egyptian pilgrims who have died during the Hajj.
Of these, 630 were undocumented in the kingdom, which distributes pilgrimage visas by country based on a quota system.
Egypt’s cabinet, which on Thursday announced a crisis unit to investigate, said 28 deaths had been confirmed from a group of 50,752 officially registered Egyptian pilgrims.
It gave no figure for the deaths of unregistered pilgrims.
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Ten countries have reported a total of 1,081 deaths during the annual pilgrimage – one of the five pillars of Islam.
The figures come from official statements or from diplomats working on responses in their countries.
Pilgrims have used umbrellas to protect themselves from the sun, as Saudi authorities warned them to stay hydrated and avoid being outdoors during the hottest hours – between 11am and 3pm.
Stampedes, tent fires, and other accidents have caused hundreds of deaths during the Hajj in the past 30 years. Some 240 people reportedly died last year.
A man uses a colourful umbrella to protect himself from the sun in Athens. Pic: AP
High temperatures on four continents
It is not only Saudi Arabia that is experiencing intense heat – with very high temperatures affecting cities on four continents.
Countries around the Mediterranean have been sizzling – with forest fires breaking out in Portugal and Greece and along the northern coast of Africa in Algeria, according to the US National Oceanic and Atmospheric Administration’s Earth Observatory.
A woman cools off at the Fontana della Barcaccia at the Spanish Steps in Rome. Pic: Reuters
In Serbia, meteorologists are forecasting temperatures of about 40C (104F) this week as winds from North Africa push a hot front across the Balkans.
Emergency services in Belgrade said doctors were called out 109 times overnight to treat people with chronic health conditions, including heart problems.
Two brothers in Washington DC. Pic: Reuters
In the United States, cooling centres are being opened for the first time this year in New York City.
In parts of Arizona, including Phoenix, temperatures were expected to reach 45.5C (114F) on Thursday.
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In India, New Delhi registered its warmest night in at least 55 years on Wednesday, with the Safdarjung Observatory reporting a temperature of 35.2C (95.4F) at 1am.
The last 12 consecutive months have ranked as the warmest on record in year-on-year comparisons, according to the European Union’s climate change monitoring service.