By Asma Alsharif
JEDDAH, Saudi Arabia (Reuters) - Saudi King Abdullah has had a successful back operation in Riyadh on Monday, the royal court of the world's top oil exporter said in a statement.
The monarch is in his late 80s and has introduced cautious reforms since becoming king in 2005. He went into the King Abdulaziz Medical City in the capital Riyadh late on Sunday for an operation to tighten the ligaments around his third vertebra.
"The surgery, thanks be to God, was successful," the royal court statement, carried by the Saudi state news agency, said.
Second Deputy Prime Minister, Prince Nayef, chairing the weekly cabinet meeting on Monday, told the ministers that the king was in "good health" after the surgery, SPA said.
Saudi stability is of global concern. A key U.S. ally, the top OPEC producer holds more than a fifth of world oil reserves and is the birthplace of Islam.
Unlike in European monarchies, the line of succession does not move directly from father to eldest son, but has moved down a line of brothers born to the kingdom's founder King Abdulaziz Ibn Saud, who died in 1953.
Abdullah -- who had already ruled as de facto regent since King Fahd suffered a stroke in 1995 -- had two rounds of back surgery in the United States last year after suffering a herniated disc, leading to a three-month recuperation period outside the kingdom.
The royal court did not say in its statement whether Abdullah would again require a period of recuperation.
Abdullah's immediate heir, Crown Prince Sultan, who is also in his mid 80s, has been in the United States since June for medical treatment.
The next-in-line after Sultan is assumed to be Prince Nayef, the interior minister since 1975, who is in his late 70s and has a reputation as more conservative than his elder brothers.
Nayef was made second-deputy prime minister in 2009 and has assumed day-to-day control of the kingdom before, during concurrent absences of his two elder brothers Abdullah and Sultan.
The leader of the West's foremost Gulf ally has given Saudi backing to U.S.-led efforts to confront and constrain Islamist militant groups, including al Qaeda, and has pushed Washington to support greater rights for Palestinians.
He has brought about reforms aimed at liberalizing the economy, giving greater technical, rather than religious, emphasis to education, and allowing women more rights.
As for the energy sector, King Abdullah is seen to have supported a moderate oil policy, raising production to prevent price spikes during supply outages from other countries.
(Reporting By Asma Alsharif; Writing By Angus McDowall; Editing by Sami Aboudi and Maria Golovnina)