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, according to state news agency SPA on Monday.

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

King Salman, the custodian of Islam’s holiest sites, spent more than two and a half years as the Saudi crown prince and deputy prime minister 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 his son, Crown Prince Mohammed bin Salman (MBS).
The crown prince has won praise at home for easing social restrictions in the conservative Muslim kingdom, giving more rights to women and pledging to diversify the economy.