World leaders are in Muscat to pay their respects to Oman's Sultan Qaboos, who died on Friday aged 79.
After sending messages of condolence on Saturday, Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, met Sultan Qaboos’ successor, Sultan Haitham bin Tariq, on Sunday.
"Today, I offered the condolences of the UAE's leadership and people to Sultan Haitham bin Tariq on the demise of Sultan Qaboos, who was a great leader with a sound vision," he wrote on Twitter after the meeting.
"May he rest in peace. May God grant Oman strength, stability and progress."
Kuwaiti Emir Sheikh Sabah, Bahrain’s King Hamad, King Abdullah of Jordan and Yemeni President Abdrabu Mansur Hadi also travelled to the capital to offer their condolences.
Sultan Haitham received leaders one after the other on Sunday, including Tunisia’s President Kais Saied, Qatar’s Emir Sheikh Tamim Al Thani and Iranian Foreign Minister Javad Zarif.
Egyptian Prime Minister Mustafa Madbouli and Palestinian President Mahmoud Abbas also travelled to Muscat to offer condolences.
Japanese Prime Minister Shinzo Abe was expected to attend – he is already in the region for a five-day tour taking in Saudi Arabia, Oman and the UAE.
The UK's Prince Charles flew overnight to the sultanate to offer his condolences, British media reported. His son, Prince William, was the last state visitor to meet Sultan Qaboos, in December.
"Prince Charles expressed his sincere condolences to His Majesty, the royal family and the Omani people for the death of the late His Majesty Sultan Qaboos bin Saeed bin Taimur," the Oman News Agency reported. The British cohort was expanded by the presence of Prime Minister Boris Johnson and the UK's Defence Minister Ben Wallace, who also visited Al Alam Palace to offer condolences.
The UK has a close strategic relationship with Oman. The late sultan shared a close friendship with the UK's Queen Elizabeth, who last visited the sultanate in 2010.
In a note of commemoration and condolence, Queen Elizabeth said Sultan Qaboos "will be remembered for his wise leadership and his commitment to peace and understanding between nations and between faiths".
"He was a good friend of my family and of the United Kingdom, and we are thankful for all he did to further strengthen the bond of friendship between our countries," she added, before offering her condolences to the Omani people.
King Willem-Alexander of the Netherlands and German President Frank-Walter Steinmeier also met with Sultan Haitham to offer condolences.
Both dignitaries and the Omani people will gather at Al Alam Palace in Muscat over the course of the three days of mourning declared upon the Sultan’s death.
On the news of his passing, world leaders praised the late sultan for the progress made by his nation over his 49-year rule.
US President Donald Trump called the sultan a friend to America who worked for peace in the Middle East.
"As the longest-serving leader in the Middle East, Sultan Qaboos brought peace and prosperity to his country and was a friend to all," Mr Trump said in a statement. Sultan Qaboos was instrumental in acting as a back channel to enable US negotiations with Iran to bring about the 2015 nucelar deal.
His funeral procession on Saturday passed along Muscat's main road amid tight security as Omanis thronged the palm tree-lined route, some reaching out their hands and others taking pictures.
The casket, draped in the Omani flag, was carried into Sultan Qaboos Grand Mosque where hundreds joined prayers inside. Sultan Haitham stood facing the casket, with the traditional curved dagger, or khanjar, strapped to his waist. Sultan Qaboos was later buried in a family cemetery.
State media did not give a cause of death. Qaboos had been unwell for years and underwent treatment in Belgium last month.