Prime Minister Dr Mahathir Mohamad had no clue what was in store when he arrived at Istana Negara in Kuala Lumpur this afternoon on official business.

The nonagenarian, who turned 94 yesterday, was pleasantly surprised when the Yang di-Pertuan Agong Al-Sultan Abdullah Ri'ayatuddin Al-Mustafa Billah Shah threw him a birthday party.

A video clip uploaded by national news agency Bernama showed palace officials rolling out two cakes while singing “Happy Birthday.”

According to a Prime Minister's Office spokesperson, one cake was made of pulut kuning while the other was fashioned as a piano topped off with a book.

The book was A Street Cat Named Bob by British writer James Bowen, published in 2010, which is Mahathir's favourite.

Yesterday, the world's oldest leader said his birthday wish is to complete his mission, which is to set the nation on the right track.

This is the second birthday Mahathir is celebrating in office after returning to power following the May 2018 general election, 15 years after his retirement.

During his first tenure, Mahathir had celebrated a total of 22 birthdays as prime minister.

His wife of more than six decades, Dr Siti Hasmah Ali, would celebrate her 93rd birthday tomorrow.