Saudi Arabia's King Salman bin Abdulaziz has been admitted to hospital, suffering from inflammation of the gall bladder, raising worries about the political fate of the world’s largest oil exporter.

King Salman, 84, who has ruled the since 2015, is undergoing medical checks in the capital, state news agency SPA said on Monday. No other details were given.

The hospitalisation prompted postponement of a visit to Riyadh by Iraqi Prime Minister Mustafa al Kadhimi.

"In recognition of the importance of the visit and a desire to make it succeed, our wise leadership in coordination with our brothers in Iraq has decided to postpone the visit," Prince Faisal bin Farhan al Saud wrote on Twitter.

MbS waits in wings

Powerful Crown Prince Mohammed bin Salman — known as MbS — is the de facto ruler and next in line to the Saudi throne.

The Crown Prince has won praise at home for easing social restrictions in the conservative Muslim kingdom, giving more rights to women and pledging to diversify the economy.

He has, however, been criticised for Saudi involvement in Yemen's civil war and attempts to silence dissident and consolidate power by marginalising rivals, including a purge of top royals and businessmen on corruption charges.

MbS’s image has also been severely tarnished following the murder of journalist Jamal Khashoggi in Istanbul in 2018 at the hands of Saudi security personnel seen as close to him.

Saudi stability is vital to the security of oil supplies since it ranks as the world’s largest oil exporter, which also keeps a significant spare capacity to ensure stable oil prices.

Kuwaiti ruler receives treatment

At the same time, the 91-year-old emir of neighbouring Kuwait underwent a “successful” surgery on Sunday that required the crown prince of the oil-rich nation to be temporarily empowered to serve in his place.

Kuwait has yet to explain why the emir, Sheikh Sabah al Ahmad al Sabah, needed to seek a previously unannounced medical treatment beginning Saturday.

Political analysts say Sheikh Sabah’s sudden surgery could renew a power struggle within Kuwait’s ruling family.

The state-run KUNA news agency described Sheikh Sabah’s hospitalisation as “medical checks,” citing a statement from the country’s royal court.

KUNA also published a report saying that the 83-year-old crown prince, Nawaf Al al-Ahmad al Sabah, had assumed some of Sheikh Sabah’s powers temporarily.