The health ministry said the total number of cases diagnosed since the virus was first recorded in the kingdom has reached 339, representing the bulk of infections registered worldwide.

Among them were four medical staff at a single hospital in Tabuk in the northwest, two doctors and two Philippine nurses.

Panic over the spread of the virus among l staff in the western city of Jeddah led to the temporary closure of a main hospital's emergency room. At least four doctors at Jeddah's King Fahd Hospital resigned this month after refusing to treat Mers patients for fear of infection.

Experts are still struggling to understand Mers, for which there is no known vaccine.

It is considered a deadlier but less-transmissible cousin of the Sars virus that erupted in Hong Kong and southern China in 2003.

Riyadh dismissed the health minister earlier this month without saying why, and Labour Minister Adel Fakieh, appointed acting health minister, promised "transparency" over Mers.

Ailing King Abdullah went to Jeddah on Thursday to reassure the public and demonstrate that "exaggerated and false rumours" about Mers were false, said his son, National Guard Minister Prince Mitab.

Fakieh said on Saturday that three specialised medical centres have been set up in Jeddah, Riyadh and Eastern Province.

Schools remain open despite rumours of possible closures, but many have asked parents to equip their children with face masks and disinfectants.

Pharmaceutical sources have already spoken of a shortage of masks in Jeddah because of rising demand.