Saudi Arabia’s health authorities are on red alert following the death of four pilgrims from swine flu, and fears this year’s Haj season could provide a breeding ground for the virus.

Health ministry spokesman Dr Khaled Marghlani told AFP that 16 other people had so far been diagnosed with swine flu and four remain in hospital in “critical condition”.

Authorities had tried to prepare for any outbreaks by installing thermal cameras at airports and ferry terminals, deploying 15,000 additional health workers and ensuring hundreds of extra beds were available.

All pilgrims now need a certificate of vaccination before they can apply for a visa to the kingdom.

The Haj, one of the five pillars of Islam, is central to the country’s tourism economy, which in turn is spearheading the kingdom’s diversification away from reliance on oil.

However, this year’s celebration, which starts today, has been plagued by fears over the swine flu as well as mounting political tensions with Iran, in particular its clergy and the president, Mahmoud Ahmadinejad, who claimed last month that the Saudi government should not host the pilgrims because of its treatment of Shiite pilgrims and alliance with the United States.

Iran banned all pilgrimages to Saudi Arabia during Ramadan in an attempt to contain the spread of the virus.

The Haj typically received 2.5 million pilgrims from across the world annually, including 200,000 from Indonesia, the largest foreign contingent. This year 20,000 health personnel have been deployed to cope with swine flu and other concerns. The Grand Mosque compound itself has capacity for 1 million pilgrims.