Brunei's Sultan Hassanal Bolkiah, recuperating in a Kuala Lumpur hospital after being treated for "fatigue", is the world's longest-reigning living monarch.

Brunei’s Sultan Hassanal Bolkiah was admitted to hospital in Malaysia due to tiredness Tuesday, though his office insisted the world’s longest-serving monarch was in “good health”.

Brunei's Sultan Hassanal Bolkiah is currently in a Kuala Lumpur hospital "resting" after feeling tired during a Southeast Asian leaders' summit, Malaysia's prime minister said on Tuesday.