Saudi royals, officials visit king in hospital after surgery JEDDAH, Saudi Arabia (Reuters) - Senior Saudi royals and government officials have visited King Abdullah in hospital, state news agency SPA reported, a week after the monarch - believed to be in his late 80s - had surgery to tighten a ligament in his back. The stability of the world's biggest oil exporter and an important regional U.S. ally is of global concern as the kingdom holds more than a fifth of the world's crude reserves and is a venue for millions of Muslim pilgrims every year. SPA's report on Saturday carried a photograph of officials and royals gathered inside the National Guard's King Abdulaziz Medical City in Riyadh, but did not say who was allowed to see the king or when he is expected to leave hospital. The king was admitted for surgery on November 16 and an announcement from the Royal Court said that he had undergone a successful back operation that lasted for 11 hours. No photographs of Abdullah have been released. Saudi analysts said on Saturday it was understandable that he would take time to recover, given his age. Abdullah underwent a similar operation in October last year and had back surgery twice in the United States in 2010 for a herniated disc, after which spent three months outside Saudi Arabia recuperating. After his back operation last year, Abdullah appeared on state television two days after his surgery and was released from hospital within five days of the operation. Investors attributed Saudi stock market selling last week to worries over the king's health. The benchmark index fell 3 percent in the trading week ending on Wednesday and fell 1.4 percent on Sunday after a 0.8 percent bounce on Saturday. The crown has passed down a line of the sons of the kingdom's founder King Abdulaziz Ibn Saud, who died in 1953. Abdullah - who took power in 2005 - named his brother Prince Salman, 13 years his junior, heir apparent in June after the death of Crown Prince Nayef bin Abdulaziz. Salman, who deputizes for the king, was shown on television last week meeting visiting U.S. officials. He also chaired the weekly cabinet meeting last Monday. Reporting by Asma Alsharif; Editing by Louise Ireland and Sami Aboudi