More than a million pilgrims joined Islam’s most important rite under a beating sun on Wednesday, as the Haj kicked off with the Saudi hosts scrambling to avoid last year’s 1,000-plus deaths in sweltering heat.

With the temperature expected to top 40 degrees Celsius, robed pilgrims slowly circled the Kaaba at the heart of Makkah’s Grand Mosque.

State media reported that others had begun arriving in the tent city of Mina on Makkah’s outskirts where they will stay overnight before the Haj’s high-point on Thursday — prayers on Mount Arafat, where the Holy Prophet Muhammed (Peace be upon him) delivered his final sermon.

About 1.4 million pilgrims arrived in Saudi Arabia ahead of the Haj.

Authorities have ratcheted up heat protection measures such as extra shade to avoid a repeat of last year, when 1,301 people died as temperatures hit 51.8C.

On Wednesday, pilgrims will perform the tawaf — walking seven times around the Kaaba.

Pilgrims arriving on buses had begun already trickling into Mina on Tuesday afternoon, greeted by staff offering them coffee and dates.

“I am so happy, it’s such an amazing feeling,” said Reem al-Shogre, a 35-year-old Saudi performing the pilgrimage for the first time.

Following last year’s lethal heatwave, authorities have mobilised more than 40 government agencies and 250,000 officials to improve protection.

Shaded areas have been enlarged by 50,000 square metres (12 acres), thousands of additional medics will be on standby and more than 400 cooling units will be deployed, Haj Minister Tawfiq al Rabiah told AFP last week.

Artificial intelligence technology will help process the deluge of data, including video from a new fleet of drones, to better manage the massive crowds.

Authorities said most of the deaths last year were among unregistered pilgrims who lacked access to air-conditioned tents and buses.

This year, they have cracked down on the unregistered, using frequent raids, drone surveillance and a barrage of text alerts.

Haj permits are allocated to countries on a quota basis and distributed to individuals by lottery. But even for those who can obtain them, the steep costs prompt many to attempt the Haj without a permit, even though they risk arrest and deportation if caught.

Large crowds at Haj have proved hazardous in the past, most notably in 2015 when a stampede during the “stoning the devil” ritual in Mina killed up to 2,300 people in the deadliest Haj disaster.