Makkah - More than two million Muslims from around the world began the Haj pilgrimage Wednesday, a religious duty and an epic multi-stage journey.

This year sees pilgrims from Iran return to Makkah in Saudi Arabia after a hiatus following a diplomatic spat between the regional rivals and a deadly stampede in 2015.

It also comes with the Gulf mired in a major political crisis that has seen thousands of faithful who would usually make the journey from neighbouring Qatar stay away.

On the esplanade of Makkah's Grand Mosque, the excitement was palpable as crowds from all four corners of the world gathered for a pilgrimage that all able Muslims are required to perform at least once in their lives.

Tidjani Traore, a public service consultant from Benin, said he was on his 22nd pilgrimage at the age of 53.

"Every time, there are new emotions," he said. "There are new innovations for organising and hosting the pilgrims. Now, for example, the tents are air-conditioned." Wearing the simple garb of the pilgrim, the faithful waited at dawn with their suitcases for buses to take them to Mina five kilometres to the east.

There, hundreds of thousands will gather before setting off on Thursday at dawn to climb Mount Arafat, the pinnacle of the Haj.

First, however, they must perform a ritual walk known as the tawaf seven times around the Holy Kaaba.

"I still have to finish the tawaf!" said a breathless Nour, 30, from Saudi Arabia as she rushed past without stopping.

Sitting on a folding chair in the middle of the esplanade, Risvana cradled her six-month-old baby who is accompanying her on the pilgrimage. "I've planned everything for him," said the young mother, pointing to a bottle of water in her bag.

Saudi authorities have mobilised vast resources including more than 100,000 security personnel to avoid a repeat of the stampede in 2015 in which nearly 2,300 people were killed. Iran alone reported 464 deaths - the highest toll among foreigners.

Although Saudi Arabia relaxed entry restrictions across its land border with Qatar two weeks before the Haj, Qatar said only a few dozen of its nationals were able to join the pilgrimage.

On the esplanade of the Grand Mosque, Saudi authorities had placed misting fans to take the edge off the intense heat.

On the eve of the first rites of the pilgrimage, the walkways thronged with people and the smell of musk wafted through the air.

Sitting in the shade of trees or reinforced concrete bridges, the faithful waited patiently for the next call to prayer.

Others continued their march, protected by a prayer mat or a small umbrella fixed on the head with an elastic band.

Several times throughout the day, well-run teams of employees, mostly Asian, cleaned the esplanade with jets of water.

As the hour for prayer arrived, a young woman sat at a table in an ice cream shop and prayed, her hands crossed on her knees.

A few paces from the Kaaba, Egyptian pilgrim Fatiya Taha could not hide her joy. At 67 the oldest in her group, she sat in her wheelchair in Islam's most holy spot. "I've been looking forward to this pilgrimage for four years," she said.