King Salman will undergo a treatment programme at Al Salam Palace in Jeddah for a lung inflammation, the state news agency said on Sunday, hours after he underwent medical tests.
Citing the royal court, the state news agency said the 88-year-old king would be treated with antibiotics until the inflammation subsides.
Due to King Salman's health issue, Crown Prince Mohammed bin Salman postponed a visit to Japan that had been scheduled to begin on Monday, Japan's Chief Cabinet Secretary Yoshimasa Hayashi said.
Earlier on Sunday, King Salman underwent medical tests at the royal clinics at Al Salam Palace due to "high temperature and joint pain", the state news agency said.
The king was last admitted to hospital in April for a routine checkup, state TV reported then.
King Salman, the custodian of Islam's holiest sites, became ruler of the world's top oil exporter in 2015 after spending more than 2-1/2 years as the crown prince and deputy premier.
Eight Israeli airstrikes have hit the Abu al-Duhur military airbase in northwestern Syria early on Tuesday, targeting the runway and storage facilities, Syria's state-run Ekhbariya said, citing a military source.
Two students were killed in a shooting at a high school in the southern Philippines on Tuesday, one of them the gunman, officials said, in the second such incident in the country in less than two months.
The Supreme Court of Pakistan has ordered on Tuesday that former Prime Minister Imran Khan be moved to hospital from jail, his Pakistan Tehreek-e-Insaf party said, meeting a longstanding demand of his party and family, who had raised concerns about his health.
A Russian missile attack has killed 10 people and injured a further eight in a village in Ukraine's northeastern Kharkiv region, the regional governor said on Tuesday.
President Donald Trump said on Monday Iran would not make the deal he thinks is needed to end a war with the US and should surrender as talks between the countries remained stalled.