Cambodian government spokesman Khieu Kanharith made the announcement on Monday, saying King Norodom Sihanouk, a widely respected figure through decades of turmoil, died of natural causes at a Beijing hospital, AFP reported.
Prince Sisowath Thomico, a royal family member who was also Sihanouk’s assistant, said the monarch suffered a heart attack at the hospital.
Sihamoni and Prime Minister Hun Sen are to fly to Beijing on Monday to collect Sihanouk's body for a traditional funeral.
The ex-monarch had been a frequent visitor to China, where he received medical treatment for cancer and diabetes, among other ailments.