Crown Prince Mohammed bin Salman, King Salman
© Amr Nabil/APFILE: The 84-year-old King Salman's ascension to the throne in 2015 ushered in the rise of his son, Crown Prince Mohammed bin Salman, to power. Saudi King Salman bin Abdulaziz gives virtual speech during an opening session of the 15th annual G20 Leaders' Summit in Riyadh
Saudi King Salman will undergo treatment 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, the de facto Saudi leader, postponed a visit to Japan that had been scheduled to begin on Monday, Japan's Chief Cabinet Secretary Yoshimasa Hayashi said.

Comment: This would be the 2nd scheduled visit abroad the prince has cancelled in the last month. With the first one, to Pakistan, cancelled prior to the King's diagnosis and hospitalisation, but after the rumour assassination attempt.

"Saudi Arabia informed the Japanese government that due to the health condition of King Salman of Saudi Arabia, Crown Prince Mohammed's visit to Japan, which had been scheduled to begin on the 20th, had to be postponed," Hayashi said at a news conference in Tokyo.

Earlier on Sunday, King Salman underwent medical tests at the royal clinics at Al Salam Palace due to "high temperature and joint pain", the Saudi state news agency said.

The king was last admitted to hospital in April for a routine checkup, state TV reported then.

Comment: Could it be that this 'routine check up' was more serious?

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.

His illness struck just as the crown prince met with U.S. National Security Adviser Jake Sullivan in the kingdom for talks on a strategic agreement between Washington and Riyadh.

Saudi Arabia's embassy in Japan did not immediately respond to a request for comment about the crown prince's cancelled trip. He had been set to meet with Japanese Emperor Naruhito and Prime Minister Fumio Kishida during the trip scheduled from May 20-23.