His cousin, culture minister Haitham bin Tariq, was sworn in as a royal ruler.
Qaboos died on Friday at the age of 79. He had been ill for some time and was believed to be suffering from colon cancer, traveling to Belgium for medical treatment in early December.
In a region rife with sectarianism, political divides, and foreign interference, the soft-spoken, diminutive Qaboos championed a foreign policy of independence and nonalignment. He became a rare leader who maintained ties with a wide range of powers that hated one another, including Iran, Israel, the United States, Saudi Arabia and the Houthi rebels in Yemen.
That gave Oman a role akin to a Middle Eastern Switzerland, where foes battling each other elsewhere could meet for quiet talks. In 2011, Qaboos intervened to free three American hikers who had been jailed in Iran on espionage charges, paying a ransom of $500,000 per person.
“The Sultan of love and wisdom has passed,” said Sheikh Mohammed bin Rashid on Twitter: “Our condolences to the people of Oman, and wish that God give them patience during their time of mourning.”
The UAE President Sheikh Khalifa bin Zayed has also ordered a three-day mourning period, starting on Saturday, and that the national flag to be flown at half-mast at all government departments across the country and at all embassies and diplomatic missions overseas.
The Crown Prince of Abu Dhabi and Deputy Supreme Commander of the UAE Armed Forces Sheikh Mohamed bin Zayed sent out a message of condolences to the people of Oman, saying: “Oman has lost a great and wise leader in Sultan Qaboos. A brother and companion of the late Sheikh Zayed. May God rest his soul.”