KUALA LUMPUR: Brunei鈥檚 Sultan Hassanal Bolkiah was admitted to the National Heart Institute in Kuala Lumpur on Tuesday due to fatigue, Malaysian government sources confirmed to AFP.

The sultan is in Kuala Lumpur with other Association of Southeast Asian Nations (ASEAN) leaders, who are meeting on Tuesday with Chinese Premier Li Qiang and dignitaries from the Gulf Cooperation Council (GCC).

鈥淗e was hospitalized in between the ASEAN-GCC and ASEAN-GCC-China summit,鈥� a source told AFP.

鈥淭he National Heart Institute is the designated hospital for VIPs during the course of this ASEAN summit and relevant meetings.鈥�

The hospital said it could not comment, but another Malaysian government source separately confirmed the news to AFP.

AFP has contacted Brunei鈥檚 embassy in Malaysia for comment.

Sultan Hassanal, 78, ascended the throne in 1967.

He is the world鈥檚 longest-reigning monarch and one of the richest people on the planet.

He comes from a family that has ruled Brunei, a small Muslim nation perched on the north of the tropical island of Borneo, for more than 600 years.

His decades ruling Brunei have seen the country gain full independence from Britain and living standards soar to among the highest globally.

But his reign has also been marked by controversies including the introduction of tough Islamic laws legislating penalties such as severing of limbs and death by stoning.