Oman’s Sultan Qaboos bin Said, the longest serving Arab leader, was laid to rest in the Royal Family Cemetery in the city of Bausha on Saturday, a day after he died, Times of Oman reported.

Prime Minister Narendra Modi was among the world leaders who expressed their condolences. “I am deeply saddened to learn about the passing away of His Majesty Sultan Qaboos bin Said al Said,” Modi tweeted. “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.”

Modi said the sultan was a true friend of India. “I will always cherish the warmth and affection I received from him. May his soul rest in peace,” he added.

At the time of death, Qaboos did not have children or a direct heir. Sultan Haitham bin Tariq al Said was named the new sultan, and the Omani government declared three days of national mourning, Al Jazeera reported.

“The funeral was led by His Majesty the Sultan Haitham bin Tariq al Said, and was attended by their Highnesses and members of the royal family, and military leaders, members of the State Council and members of the Shura Council,” Oman News Agency said in a statement. “The funeral prayer was held at the Sultan Qaboos Grand Mosque, where the Sultan’s body was wrapped with the national flag.”

Qaboos bin Said was 79, and ruled Oman for five decades since overthrowing his father in a bloodless coup in 1970. Though the announcement about his death did not mention the cause, Qaboos had been receiving cancer treatment in Europe since at least 2014, according to The New York Times.

Qaboos was revered in his country for using oil wealth to pull it from poverty. Roads, a port, a university, and a sports stadium are some of the things that bear his name. He was instrumental in bringing together Iran and the United States for covert talks that led to an international agreement about Iran’s nuclear programme, limiting Tehran’s chances developing a nuclear bomb. However, the Donald Trump administration pulled the country out of the deal, and in recent weeks ratcheted up tensions with Iran.