RIYADH (AFP) - Saudi King Abdullah, hospitalised earlier this week, is suffering from pneumonia and breathing with the aid of a tube, but is in stable condition, the royal court said on Friday.
The long-ailing king, who is believed to be around 90 years old, was admitted to the King Abdulaziz Medical City in Riyadh on Wednesday for checks.
Examination "revealed pneumonia, which required the provisional insertion of a tube on Friday evening", a statement said.
"Thanks be to God, that step was crowned with stability and success," the statement added, without saying how long the king would need to remain in hospital.
In recent years, his advanced age and poor health have raised concerns about the future leadership of one of the world's key oil producers.
King Abdullah's half-brother, Crown Prince Salman, 77, is next in line to the throne. He was named crown prince in June 2012 following the death of Prince Nayef bin Abdul Aziz.
Prince Salman has been representing the king at most recent public events, including last month's Gulf summit in Qatar, because of the monarch's ailing health.
The Saudi stock market dropped by about 5 per cent at one point following the royal court's announcement that the king had been hospitalised, before clawing back some of its losses to finish Wednesday at 1.8 per cent lower.
The market was closed for the weekend on Friday.
The king's latest hospitalisation comes as Saudi Arabia holds a high-profile position in the US-led fight against the Islamic State group, which has seized swathes of neighbouring Iraq and Syria.
Saudi warplanes have joined in coalition air strikes against Islamic militants in Syria, although the ultra-conservative Muslim kingdom has faced calls to do more to halt the flow of funds and fighters to Islamic State in Iraq and Syria (ISIS) from among its own citizens.
The king's absence from the public gaze for some time last year prompted rumours on social media networks that his health was deteriorating.
He underwent two operations in October 2011 and November 2012 to correct "ligament slackening" in the upper back.
Since the death in 1952 of King Abdul Aziz al-Saud, the founder of Saudi Arabia, the throne has systematically passed from one of his sons to another, brothers and half-brothers.
But many of King Abdul Aziz's sons are old or have died. King Abdullah's former crown princes, Sultan and Nayef, died in 2011 and 2012 respectively.
In March 2014, King Abdullah named his half-brother, Prince Moqren, as a second crown prince, in an unprecedented move aimed at smoothing succession hurdles.
Prince Moqren, who was born in 1945, is the youngest of King Abdul Aziz's sons.