Swine flu has killed four pilgrims in Saudi Arabia for the annual Hajj, health authorities said on Saturday only a few days before the massive Muslim gathering reaches its peak.
An Indian man, a Moroccan woman and a Sudanese man -- all aged 75 -- died from A(H1N1), as had a 17-year-old girl from Nigeria, Saudi health ministry spokesman Khaled al-Marghlani said.
"They all had pre-existing conditions," including the Nigerian woman who had a chest-related problem, Marghlani told AFP.
"Also, none of them took the (H1N1) vaccine," he added.
An estimated 2.5 million Muslims are expected to converge in Saudi Arabia for this year's Hajj, making it the world's largest gathering since swine flu began spreading around the globe after it was first reported in April.
The fatalities in Saudi Arabia were the first among pilgrims to the holy cities of Mecca and Medina since the outbreak of swine flu, out of 20 proven cases.
Twelve infected pilgrims have been released after treatment, while four remain in hospital.
Health professionals say the infection figure remains lower than expectations ahead of the Hajj, but the disease has spread among the general population of Saudi Arabia much as it has elsewhere.
On November 11, the Saudi authorities reported 70 people had died in the country from swine flu and that more than 7,000 proven cases had been recorded.
Muslims are obliged to undertake the pilgrimage once in their lifetime if they have the means.
People at risk of suffering severe consequences from swine flu -- including children, pregnant women, the elderly and individuals with chronic diseases -- have been urged to postpone going on the Hajj in 2009.
But an estimated 1.5 million pilgrims from across the globe have already descended on western Saudi Arabia, and another one million are expected when the rites begin on Tuesday.
Authorities are using thermal cameras to check all arrivals for signs of infection at the air and sea terminals in Jeddah where most pilgrims arrive.
Some 20,000 health workers are deployed in Mecca, Medina and Jeddah, and hospitals have hundreds of extra beds available.
The health ministry has deployed mobile units throughout Mecca and Medina which can instantly send to a central monitoring centre the locations of infections, to monitor outbreaks.
The also have in key locations equipment which can positively identify the virus in a person suspected of infection within a few hours.
Still, despite widespread warnings, less than 20 percent have received H1N1 vaccinations prior to their arrival, according to Saudi health workers.
Fears of contagion are expected to rise when pilgrims mass on Mount Arafat, where the Prophet Mohammed gave his final sermon, on November 26, and then at the Jamarat in Mina over the next days where all partake in a ritual stoning of the devil.
While the Hajj ends on November 29, hundreds of thousands of pilgrims will remain in the area for several weeks before heading back to their countries, heightening the risk of H1N1 cross-border transmission.
On Friday, World Health Organisation data showed around 6,750 people had died from swine flu worldwide since the virus was first uncovered in Mexico and the United States in April.