British Prime Minister Boris Johnson and Prince Charles were among those who arrived in Muscat to meet Oman's new ruler, Sultan Haitham bin Tariq Al Said.
Other leaders included Kuwait's ruling emir, Sheikh Sabah Al Ahmad Al Sabah, as well as Qatar's ruling emir, Sheikh Tamim bin Hamad Al Thani.
Bahrain's King Hamad bin Isa Al Khalifa and the president of Yemen's internationally recognised government, Abed Rabbo Mansour Hadi, also visited.
Sultan Haitham was Oman's culture minister before being named as the successor to Sultan Qaboos, the Middle East's longest-ruling monarch whose death was announced Saturday. He died at the age of 79 after years of an undisclosed illness.
Sultan Haitham, 66, has pledged to follow Sultan Qaboos' example of promoting peace and dialogue in the Mideast.
Oman has served as an interlocutor between Iran and the US, which are facing a level of unprecedented tensions. Iran's Foreign Minister Mohammad Javad Zarif travelled to Muscat on Sunday as well to meet Sultan Haitham.
Oman sits on the eastern edge of the Arabian Peninsula.