Saudi Arabia’s 84-year-old ruler, King Salman bin Abdulaziz, has been admitted to hospital in the capital Riyadh, suffering from inflammation of the gall bladder, state news agency SPA said on Monday.

The king, who has ruled the world’s largest oil exporter and close US ally since 2015, is undergoing medical checks, the agency added, without giving details.

After the news, Iraqi Prime Minister Mustafa al-Kadhimi postponed a visit scheduled to Saudi Arabia, said foreign minister Prince Faisal bin Farhan Al Saud said.

King Salman, the custodian of Islam’s holiest sites, spent more than two-and-a-half years as the Saudi crown prince and deputy Premier from June 2012 before becoming king. He also served as governor of the Riyadh region for more than 50 years.

The de facto ruler and next in line to the throne is the crown prince, Mohammed bin Salman, widely referred to as MBS, who has launched reforms to transform the kingdom’s economy and end its “addiction” to oil.

The 34-year-old prince, who is popular among many young Saudis, has won praise at home for easing social restrictions.