Sultan Qaboos bin Said of Oman has died, according to an announcement by Omani state television and the state news agency early on Saturday.
"With sadness ... the Omani Sultanate court mourns ... our Sultan Qaboos bin Said ... who God chose to be by his side on Friday evening," the agency said.
It added that Qaboos died after "a wise and triumphant march rich with generosity that embraced Oman and extended to the Arab, Muslim and entire world, and achieved a balanced policy that the whole world respected".
A three-day period of mourning has been declared in Oman and the country's flag will be flown at half-mast for 40 days.
Qaboos's funeral procession began in the capital, Muscat, as thousands gathered in the streets leading up to the Sultan Qaboos Grand Mosque where prayers were held before noon, ahead of his burial.
Later on Saturday, Oman named Haitham bin Tariq Al Said as the country's new ruler, Omani state television announced.
The former culture minister, 65, has been sworn in before the ruling family council on Saturday morning.
State television said authorities had opened a letter by Qaboos naming his successor, without elaborating, before announcing Haitham bin Tariq as the new ruler., the longest-ruling Arab monarch, had been ill for some time and was believed to have been suffering from colon cancer.
The sultan, 79, had ruled Oman since overthrowing his father in a bloodless coup in 1970.
Since assuming power, Qaboos transformed Oman from an isolated backwater, with little or no infrastructure, into a modern state.He had recently returned to Muscat after seeking medical treatment in Germany and Belgium. But his prolonged absences for treatment stirred questions about succession in the country of 4.5 million people.
Transition of power
In October 2011, Qaboos, who has no children or brothers, amended the process of succession. But he had not publicly announced who that successor would be.The sultan, whose closest relatives are his cousins, appointed five top officials to a council that would be involved in confirming the new sultan in case of any royal family dispute.
Under Omani law, if the royal family failed to agree on a successor, the position would then go to the person whose name is in two sealed letters written by Qaboos.
Oman observers had said the sultan's three cousins - Assad, Shihab and Haitham bin Tariq Al Said - stood the best chance.
"I imagine that the succession itself will be a smooth process within Oman," Kristian Coates Ulrichsen of the Texas-based Rice University's Baker Institute told Reuters news agency.
"Sultan Qaboos had such charismatic authority and became so synonymous with Oman as a modern nation-state that it will naturally be difficult for any successor to replicate that, at least at the beginning."In the United Nations, the death leaves a political vacuum not just in his country but also in the region.
"He is a very big loss in the region. Oman played an outsized role in the region, particularly in the Gulf and the wider Middle East," Bays said, pointing out that Qaboos played a crucial role in secret negotiations leading to the 2015 Iran nuclear deal.
"I think people are worried particularly at this time of turbulence, at a time when relations between the US and Iran are so bad, when in recent days the two countries have seen come so close to war."
Bays also noted that the death of Qaboos comes at a time when the Gulf Cooperation Council has become deeply divided following the Saudi Arabia-led blockade against Qatar.
