Saudi King Abdullah left hospital on Thursday, nearly a month after undergoing back surgery, the royal court announced. The 89-year-old monarch left the King Abdulaziz Medical City in Riyadh on Thursday afternoon, the court said in a statement carried by the official SPA news agency. On November 18, the royal court announced that Abdullah had undergone an operation to correct \"a ligamentary slackening in the upper back.\" He appeared on state television on November 28 for the first time after the surgery, sitting in a wheelchair to receive royal dignitaries in his hospital suite. He has made no further appearances since then. The king\'s absence from the public gaze had sparked growing rumours about his health on social networking website Twitter. The king had a similar operation in October 2011. In November 2010, he underwent surgery in New York for a slipped disc, complicated by a blood clot that put pressure on his spine. He then had a further operation that December before convalescing for a month in Morocco. The king\'s age and frequent hospitalisations have raised concerns about the future leadership of the world\'s key oil producer. The heir to the throne is his half-brother Crown Prince Salman, 76, who was named to the succession on the death of Prince Nayef in June.