Leaders from around the world have paid tribute to Oman's Sultan Qaboos bin Said, whose death was announced on Saturday morning.
Sultan Qaboos had ruled Oman for almost 50 years, coming to power in 1970, and drove a widespread programme of modernisation in the country throughout those five decades and favoured moderation and mediation in regional affairs.
He is succeeded by Sultan Haitham bin Tariq Al Said, who was sworn in earlier today.
In the UAE, three days of mourning were announced by President Sheikh Khalifa.
Sheikh Khalifa commended the late Sultan for being dedicated to the service of his people, state news agency WAM reported.
Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, described Sultan Qaboos as "the sultan of love" and extended the country's "condolences to the people of Oman".
Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, wrote that "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."
“Today we lost a historic and renaissance figure of high class with the death of Sultan Qaboos,” UAE’s Minister of State or Foreign Affairs Anwar Gargash wrote on Twitter.
Saudi King Salman and Crown Prince Mohammed bin Salman sent their condolences for the passing of Sultan Qaboos. A royal statement said that Saudi Arabia and its people share the grief of the people of Oman.
Bahrain has announced it has also begun a period of three days of mourning.
Jordan's King Abdullah said on Twitter that "we have lost ... a dear friend of my father the late King Hussein and supporter of Jordan in defending Arab and Islamic causes."
Egypt's president Abdel Fattah El Sisi, extended his "sincere condolences to the Arab nation and the brotherly Omani people" and hailed Sultan Qaboos as a "constant supporter of Arab and Islamic issues".
Rashtrapati Bhavan, president of India, called Sultan Qaboos "a close friend of India" and noted that the world had lost "a great leader and a statesman who worked tirelessly towards building peace in the region and the world."
India's prime minister Narendra Modi said he was "deeply saddened" by the news of Sultan Qaboos's death.
"He was a visionary leader and statesman who transformed Oman into a modern and prosperous nation. He was a beacon of peace for our region and the world."
Imran Khan, Pakistan's prime minister, commented that "Oman has lost a beloved leader and Pakistan a close, trusted friend".
Iranian foreign minister Mohammad Javad Zarif described Sultan Qaboos's death "a loss for the region".
Earlier former US president George W Bush issued a statement recognising Sultan Qaboos as "a stable force in the Middle East and a strong US ally". He also noted that the late leader had a clear vision for a "modern, prosperous, and peaceful Oman" and he "willed that vision into reality."
Elsewhere, UK prime minister Boris Johnson said on Twitter that he was struck by Sultan Qaboos's "commitment to peace and understanding between nations and between faiths. He leaves a profound legacy, not only in Oman but across the region."
Former UK prime minister Tony Blair said he felt "great sadness" when he heard the news.
"He was a leader of vision and purpose who took over the leadership of his country at a difficult time and raised it to an entirely new level of development and prosperity. He was a man of culture, humanity and deep conviction who strove to make his nation and the world better and more peaceful. He was kind, thoughtful and with a big heart. He had great wisdom and insight from which I benefited often as did so many others. My deepest sympathy, prayers and condolences are with the people of Oman. He will be sorely missed.”