Saudi Arabia's 84-year-old ruler King Salman underwent successful surgery Thursday to remove his gall bladder, the royal court said, three days after he was admitted to hospital.

It is rare for Saudi Arabia to report on the health of the ageing monarch, who has ruled the top oil exporter and the Arab world's biggest economy since 2015.

The king is the second reigning monarch in the Gulf to be hospitalised after Kuwait's 91-year-old emir Sheikh Sabah al-Ahmad Al-Sabah, amid the twin regional crises of the coronavirus pandemic and a plunge in crude prices.

The king "underwent a laparoscopic surgery to remove the gall bladder today... at King Faisal specialist hospital in Riyadh," the royal court said in a statement carried by the official Saudi Press Agency.

The king will remain in hospital for some time after the "successful" surgery, the statement added.

The monarch was admitted to hospital on Monday "for some medical tests" due to inflammation of the gall bladder, according to the royal court.

The king's hospitalisation prompted Iraqi Prime Minister Mustafa al-Kadhemi to postpone his scheduled visit to Saudi Arabia, which was due to start on Monday.

A video released by state media on Tuesday showed the king chairing a virtual cabinet meeting from hospital.

The soundless video was apparently aimed at dispelling rumours about the king's health.

In 2017, Saudi Arabia dismissed reports and mounting speculation that the king was planning to abdicate in favour of his young son, Crown Prince Mohammed bin Salman, who is widely seen as the de facto ruler.

Under the king's rule, Saudi Arabia has launched ambitious economic reforms for a post-oil era and given more rights to women, but also adopted a more assertive foreign policy and entered a war in neighbouring Yemen.