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 U.S. ally since 2015, was undergoing medical checks, the agency added, without giving details.
King Salman, the custodian of Islam's holiest sites, spent more than 2-1/2 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 defacto ruler and next in line to the throne is the crown prince, Mohammed bin Salman , widely known by his initials 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 young Saudis, 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.
To the king's supporters, this boldness at home and abroad was a welcome change after decades of caution, stagnation and dithering.
But state control of the media and a crackdown on dissent in the kingdom make it difficult to gauge the extent of domestic enthusiasm.