The Istana Negara in a statement yesterday announced that the Sultan of Kelantan, Sultan Muhammad V had stepped down as the 15th Yang di-Pertuan Agong effective the same day but did not mention any reason for the resignation.
Although the functions of the king are largely ceremonial, he also serves to safeguard Islam in Muslim-majority Malaysia, and must assent to the appointment of individuals for various senior government roles including that of prime minister.
In his statement, the 49-year-old expressed his gratitude to the Malay Rulers, who elected him in 2016.
It follows weeks of speculation after the royal took medical leave, followed by online rumours and pictures purported to show him marrying a former Miss Moscow in Russian Federation.
Watch: Malaysia's king abdicates.
Rumours had been swirling that the king might step down after a rare meeting was convened amongst the country's nine state rulers recently.
Malaysia's royal families have met to decide when a new king will be elected from among them after King Muhammad V unexpectedly resigned, according to the country's national news agency Bernama.
Amad Faizal said: "The Sultan is a caring Ruler who only has the people's interest in his heart".
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He made an early exit from their 2-0 Premier League defeat to Crystal Palace but is now fully fit and available. Is he exactly the player [he was] in his best time at Leipzig? He's still adapting, that's how it is.
Royal officials in Malaysia have so far not commented on the rumoured marriage, or given any details about the state of the king's health.
The rotating monarchy system has been in place since independence from Britain in 1957, and Sultan Muhammad V is the first monarch to have renounced the throne.
Malaysia has nine royal households, who typically take turns to sit on the throne.
Permatang Pauh MP Nurul Izzah Anwar thanked Sultan Muhammad V for giving a full pardon to her father, Datuk Seri Anwar Ibrahim.
Sultan Muhammad V's resignation was in accordance with Article 32 (3) of the Federal Constitution, comptroller of the Royal Household Wan Ahmad Dahlan Ab Aziz said.
Despite the images, Prime Minister Mahathir said then that he did not have official confirmation on the wedding when questioned about it earlier this week.
Constitutional law expert Nizam Bashir Abdul Kariem Bashir told New Strait Times today that while the rules of succession are "intricate", he expects an announcement soon.