He became sultan in July 1970 after deposing his father in a palace coup with the aim of ending the country’s isolation and using its oil revenue for modernization and development.
Oman state news agency ONA said 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”.
It did not disclose the cause of death. Qaboos, 79, had been ailing for years and was in Belgium in December for treatment, according to Reuters.
His death leaves Oman without a clear successor because he never publicly named one. The sultan, who has dominated decision making in the Persian Gulf state for decades, has secretly recorded his choice in a sealed letter should the royal family disagree on the succession line.
“The appointment and blessing of a successor by the sultan while alive would have been a huge service to Oman,” said one diplomat in the region.
Analysts worry about royal family discord, and a resurgence of tribal rivalries and political instability, now a new ruler has to be chosen at a time when young hawks have assumed power in neighboring Saudi Arabia and the United Arab Emirates.
Qaboos healed old rifts in a country long divided between a conservative tribal interior and seafaring coastal region. He became known to his countrymen as “the renaissance”, investing billions of dollars of oil revenues in infrastructure and building one of the best-trained armed forces in the region.