Saudi Arabia's King Abdullah
Saudi Arabia's King Abdullah is 91-years-oldReuters

Saudi Arabia's King Abdullah ibn Abdulaziz has been admitted to hospital for "medical checks".

The 91-year-old was reportedly flown by helicopter from his desert resort to the King Abdulaziz Medical City in Riyadh.

No specified details were given about his current condition. However, he has been repeatedly hospitalised during this year and rarely makes public appearances.

In October 2011 and November 2012, the King underwent back surgery, reportedly to correct "ligament slackening" in his upper back.

Born in 1924, he was crowned king of Saudi Arabia on 1 August 2005 after his half-brother, Fahd, died at the age of 84.

Since he was crowned, the King has shown signs of relaxing strict freedoms in the Kingdom as well using Saudi's vast oil wealth to invest in education and infrastructure projects.

Despite the early promise, many Saudi women in the Kingdom have been left disappointment by the lack of women rights reforms.

Two Saudi women are currently facing possible terror charges for illegally driving inside the Kingdom.

In the summer, King Abdullah played a key part in persuading other Arab countries to join the US-led coalition air strike campaign against Islamic State.

Abdullah's half brother Salman, 77, is next in line to succeed the throne. Salman is currently Crown Prince, following the death of Prince Nayef bin Abdul aziz in June 2012.