Oman's Sultan Qaboos bin Said passed away at the age of 79 on the evening of January 10 (Friday), state media reported on the wee hours of January 11 (Saturday). Oman has announced an official three-day period of national mourning to mark the passing away of the monarch and head of state.

However, the cause of his death was not declared. State media ONA simply reported that Sultan Qaboos died following 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."

Prime Minister Narendra Modi expressed his grief in a tweet, where he described the deceased Sultan as "a true friend of India". PM Modi tweeted out from his official handle on the social media website, "Sultan Qaboos was a true friend of India and provided strong leadership for developing a vibrant strategic partnership between India and Oman. I will always cherish the warmth and affection I received from him. May his soul rest in peace."

Qaboos bin Said Al Said was the longest-serving leader in the entire Middle East and Arab states and had been ruling Oman for more than 50 years. He had come to power after ousting his father, Said bin Taimur in a bloodless coup - the 1970 Omani coup d'état, with the help of Oman's former colonial power Britain.

Since the Sultan had no children and did not publicly appoint any successor, the law states that the ruling family, the House of Al Said, will appoint a successor within three days of the throne becoming vacant, failing which a council will put in power the person whose name the Sultan had written in a closed letter.

In December, the Sultan had travelled to Belgium for what has been described as "medical checks". However, news agencies stated that even after his return, there reports of his deteriorating physical health.