Sultan Qaboos, the longest-reigning leader of the modern Arab world, has died at the age of 79, leaving Oman in search of a new ruler at a time of regional turmoil.
Qaboos, who ruled since 1970 when he deposed his father in a palace coup, had been ill for some time and had been believed to be suffering from colon cancer.
He left no apparent heir. He was unmarried and had no children or brothers and it is not clear who will succeed the sultan, whose country has a distinct method of choosing the next ruler.
"With great sorrow and deep sadness... the royal court mourns His Majesty Sultan Qaboos bin Said, who passed away on Friday," the court said in a statement, announcing a mourning period that will see businesses and government offices close for three days.
Qaboos transformed the Arabian Peninsula nation from a backwater into a modern state with a thriving tourism industry, thanks to the country's crystal waters, scenic desert and mountain ranges.
But it was the sultan's policy of neutrality and non-interference that elevated Oman's standing as a "Switzerland of the Middle East" and made him an important mediator.
Many Western and Arab diplomats see the sultanate, with its moderate but active foreign policy that includes healthy relations with the United States as well as with regional powers Iran and Saudi Arabia, as a model of balance.
The state news agency ONA said the sultan had passed away after presiding over a "renaissance" in Oman that saw it achieve prosperity and exert its influence with a "foreign policy that was saluted with solemn respect by the whole world".
As the Gulf's discreet go-between, Oman played a role in Iran's 2015 nuclear deal with world powers while preserving its membership in the Saudi-led Gulf Cooperation Council (GCC).
"He was a stable force in the Middle East and a strong US ally. His Majesty had a vision for a modern, prosperous, and peaceful Oman, and he willed that vision into reality," former US president George W. Bush said in a message of condolence.
Abu Dhabi Crown Prince Mohammed bin Zayed Al-Nahyan said Saturday morning that Oman and the Arab world have lost a "wise leader and a (figure) of great historical stature".
The sultan's death comes amid increased tensions between Tehran and Washington, who on Friday piled new sanctions on the republic following the killing of a top Iranian commander in Iraq.
The sanctions marked the latest salvo in a US-Iranian confrontation that risked sliding into war a week ago with the deadly US drone attack on general Qasem Soleimani, by some measures the second most influential person in Iran.
Secret letter
"It's almost impossible to imagine Oman without Sultan Qaboos at the helm," said Kristian Ulrichsen, a fellow at Rice University's Baker Institute in the US.
"His wise leadership and regional statesmanship is never more urgently needed than at the present time," Ulrichsen said on Twitter, adding that attention would now fall on a small group of cousins of the late leader.
According to the Omani constitution, the royal family shall, within three days of the throne falling vacant, determine the successor.
If the family does not agree on a name, the person chosen by Qaboos in a letter addressed to the royal family will be the successor.
The sultan should be a member of the royal family, as well as "Muslim, mature, rational and the legitimate son of Omani Muslim parents".
Experts say that more than 80 men meet the criteria, but one name stands out: Asad bin Tariq.
Tariq, a 65-year-old cousin of the late sultan, was appointed deputy prime minister for international relations and cooperation affairs in 2017 in what was seen as a clear message of support.
Once commander of the country's armored brigades, Asad bin Tariq served as the sultan's "special representative" since 2002, heading government delegations and receiving foreign officials.
Other potential successors include two other cousins of the sultan -- Haitham bin Tariq, 65, the heritage and culture minister, and Shihab bin Tariq, 63, who was a close adviser to the royal ruler.
Discreet mediator
During the sultan's reign, Western nations repeatedly turned to Muscat to act as a mediator in resolving thorny regional issues -- from the kidnapping of Americans and Europeans to the 2015 Iran nuclear deal.
Although it is a member of the GCC, Oman is the only Gulf country not to have taken part in the Saudi-led military coalition's fight against Yemen's Iran-backed Huthi rebels.
Unlike other Arab states, Qaboos did not contest Egypt's 1979 peace treaty with Israel, opening a trade office in Tel Aviv in the mid-1990s -- shuttered in 2000 during a Palestinian uprising.
In October 2018, Israeli Prime Minister Benjamin Netanyahu held surprise talks with Qaboos in Muscat.
It remains to be seen whether the next Omani ruler will take the same moderate approach in a region often in turmoil.
