Saudi Arabia's de facto ruler reassured the cabinet on Tuesday about the health of his ageing father King Salman, who was set to undergo another round of tests for a lung infection.

Crown Prince Mohammed bin Salman, 39, "reassured everyone about the health" of King Salman, 88, and voiced "appreciation to everyone who inquired about his health", the official Saudi Press Agency reported on Tuesday after Prince Mohammed chaired the weekly cabinet meeting.

On Sunday, state media reported that King Salman had a lung infection and would undergo tests "based on the recommendations of the royal clinics".

King Salman has been on the throne since 2015, though Prince Mohammed became first in line to the throne in 2017 and acts as day-to-day ruler.

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

The Royal Court disclosed in May that he was suffering from a lung infection, high temperature and joint pain and was undergoing a treatment programme involving antibiotics, Soon afterwards, it announced he had recovered.

King Salman last chaired a cabinet meeting on September 24.

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.