Last month he returned home after undergoing medical checks and treatment in Belgium.
At the age of 29, the sultan deposed his father in a bloodless coup with British support in 1970.
He is considered to be the pioneer in transforming Oman into a developed nation. However. Sultan Qaboos was unmarried and had no heir or designated successor. Hence, it is uncertain who would succeed him.
Three days of national mourning have been declared in view of Oman’s state leader.
In addition, the Royal Family Council should choose a new sultan within three days of the throne falling vacant.