Saudi health officials overseeing the haj pilgrimage later this week say they are prepared to handle any outbreak of disease or a stampede like the one that killed hundreds of worshippers two years ago.

Saudi Arabia said on Monday that over 1.735 million pilgrims have arrived from abroad for the ritual, a once-in-a-lifetime religious duty for every able-bodied Muslim who can afford the journey.

The world's largest annual gathering of Muslims has in the past seen numerous deadly stampedes, fires and riots, with authorities having only limited ability to control the masses.

Saudi Arabia stakes its reputation on its guardianship of Islam's holiest sites - Mecca and Medina - and organising haj, a role that Iranian authorities have challenged as part of a dispute over the handling of a crush in 2015.

That incident killed nearly 800 pilgrims, according to Riyadh, although counts by countries of repatriated bodies showed over 2,000 people may have died, more than 400 of them Iranians.

Hussein Ghanam, who oversees the health ministry's haj operations, said the authorities are prepared in case of another stampede.

"There is an integrated fleet of ambulances, each of which is considered its own fully equipped intensive-care unit. The ambulances circulates on the roads between the tents," he said.

Some 30,000 health workers will be on hand, and 5,000 hospital beds are available.

The Saudi Red Crescent is supporting the ministry with 350 ambulances and four medivac helicopters, director Mohammed bin Abdullah al-Qassim said. It has opened several new health centres this year and run simulations to practice emergency response.

"Thanks to God we have extra supplies plus special equipment and vehicles to deal with catastrophes directly and move them to the closest hospital," Qassim told Reuters on Sunday.

Nearly 90,000 Iranians are expected to attend the haj this year for the first time since the 2015 crush.


DISEASE PREVENTION

Another perennial concern is the potential for spreading disease among the pilgrims, who spend five days in close quarters with each other, often eating outside and sleeping on the ground near holy sites.

Ghanam said the ministry was prepared to control communicable diseases like the potentially fatal Middle East respiratory syndrome (MERS) coronavirus, which has been most prevalent in Saudi Arabia over the past five years.

"We have a precedent of repeated success in past years in dealing with the outbreak of corona, SARS, and swine and bird flu," he said - awareness campaigns and health requirements for pilgrims kept those outbreaks from reaching the Mecca area.

The World Health Organization (WHO) said there were 26 newly reported cases of MERS in Saudi Arabia in July and early August, including six deaths.

In addition, more than half a million people in neighbouring Yemen have been infected with cholera and 1,975 people died since an epidemic began in April in that country, according to the WHO.

Ghanam said hospitals have been directed to pay careful attention to pilgrims showing symptoms of cholera, which is spread by ingestion of food or water tainted with human faeces and can kill within hours if untreated.

Yemenis have undergone the same health checks as all other pilgrims, he said.