After being diagnosed with a lung infection, Saudi Arabia's King Salman underwent medical tests on Sunday night, the Royal Court said in the latest update on the ageing monarch's health.

King Salman "will undergo some medical tests this evening, ...based on the recommendations of the royal clinics, due to a lung infection," said the statement carried by the Saudi Press Agency on Sunday.

The 88-year-old king has been on the throne since 2015, while his son, Mohammed bin Salman, 38, was named crown prince in 2017 and acts as day-to-day ruler, AFP reported.

Saudi Arabia, the world's biggest crude oil exporter, has for years sought to quell speculation over King Salman's health.

The monarch's well-being is rarely discussed, but the Royal Court disclosed in May that he was undergoing a treatment programme involving antibiotics after he was admitted to hospital for tests. Soon after it announced he had recovered.

The previous month he was admitted for "routine examinations" and left later the same day.

Prior to that, he was hospitalised in May 2022, when he went in for a colonoscopy and stayed for just over a week for other tests and "some time to rest", the official Saudi Press Agency reported at the time.

He was also admitted to hospital in March 2022 to undergo what state media described as "successful medical tests" and to change the battery of his pacemaker.

And in 2020 he underwent surgery to remove his gall bladder.

In 2017, Riyadh dismissed reports and mounting speculation that the king was planning to abdicate in favour of Prince Mohammed.

King Salman served as Riyadh governor for decades and also as defence minister.

His reign as king has been marked by ambitious social and economic reforms largely managed by his son, who is trying to position Saudi Arabia for an eventual post-oil future.

Prince Mohammed has also overseen an intense crackdown on dissent that analysts say has helped him consolidate power.