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.
Ukraine issued air raid alerts for Kyiv and the country's eastern half as blasts shook the city of Mykolaiv early on Monday, authorities said, hours after the one-day Easter ceasefire declared by Russian President Vladimir Putin came to an end.
US Vice President JD Vance began a four-day visit to India on Monday and will hold talks with Prime Minister Narendra Modi, as New Delhi rushes to avoid steep US tariffs with an early trade deal and boost ties with the Trump administration.
The Israeli military on Sunday said a review into last month's killing of emergency responders in Gaza found there had been "several professional failures" and that a commander would be dismissed over the incident.
US President Donald Trump is threatening to cut another $1 billion in funding for Harvard University, this time targeting health research, the Wall Street Journal reported on Sunday, as the administration's row with elite schools escalated.