Norodom Sihanouk, the former Cambodian king who remained an influential figure in his country's politics through a half-century of war and upheaval, died on Monday at the age of 89.

Cambodian government spokesman Khieu Kanharith said Sihanouk died of natural causes in Beijing, where he had traveled for medical treatment earlier this year.

Prince Sisowath Thomico, a royal family member who was also Sihanouk's assistant, said the former king suffered a heart attack at a Beijing hospital.

"His death was a great loss to Cambodia,'' Thomico said, adding that Sihanouk had dedicated his life "for the sake of his entire nation, country and for the Cambodian people".

Sihanouk was a key figure in Cambodian politics for six decades before abdicating power in 2004, citing poor health. He was succeeded by a son, Norodom Sihamoni.

Sihanhouk had been in China since January, and had suffered a variety of illnesses, including colon cancer, diabetes and hypertension.

Kanharith said arrangements were being made to repatriate his body for an official funeral in Cambodia.

In January, Sihanouk requested that he be cremated in the Cambodian and Buddhist tradition, asking that his ashes be put in an urn, preferably made of gold, and placed in a stupa at the country's Royal Palace.

Sihanouk saw Cambodia transform from colony to kingdom, US-backed regime to Khmer Rouge killing fields, foreign-occupied land to guerrilla war zone, and finally to a fragile democracy.

Sihanouk was a feudal-style monarch who called himself a democrat. He was beloved by his people, but was seldom able to deliver the stability they craved through decades of violence.