Saudi Arabia’s King Salman was admitted to a hospital in Riyadh for medical tests on Monday, the state news agency SPA reported.
King Salman, 84, who has ruled since 2015, is suffering from an inflammation of the gall bladder, Spa said.
The custodian of Islam's holiest sites, he 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.
King Salman has presided over Crown Prince Mohammed bin Salman’s rapid reform plan to transform the kingdom’s economy and end its dependence on oil.
Prince Mohammed, 34, who is popular among young Saudis, has won praise at home for easing social restrictions, giving more rights to women and pledging to diversify the economy.
His Vision 2030 sets out a framework intended to steer the kingdom away from its economic reliance on hydrocarbons and develop public service sectors in fields such as health care, education, infrastructure, recreation and tourism over the next decade.