DUBAI (Reuters) - Saudi King Abdullah is in hospital in Riyadh for a back operation, the official Saudi Press Agency said Sunday.

"The custodian of the two holy mosques, King Abdullah, arrived today evening at King Abdul Aziz Medical City in Riyadh to undergo a surgery to re-tighten the binding connector around the third vertebra," the agency said in an English-language report.

The ruler of the kingdom, who is thought to be 88, suffered a herniated disc late last year requiring surgery in the United States.