(CNN) -- Former Cambodian King Norodom Sihanouk, who was monarch for more than 60 years until his abdication in 2004, died early Monday in Beijing at the age of 89, state news reported.
Sihanouk died of natural causes after having been treated by Chinese doctors for years for various forms of cancer, diabetes and hypertension, China's state-run Xinhua news agency reported, citing Cambodian Deputy Prime Minister Nhik Bun Chhay.
The "royal government" will bring the late king's body back to his homeland for a traditional funeral, according to Cambodia's official AKP news agency. Xinhua reported that Sihanouk's son, King Norodom Sihamoni, will fly to Beijing later Monday to receive his father's body for burial.
Health problems led Sihanouk to announce his abdication in October 2004 while he was in Beijing for treatment, according to the king's official website.
A panel elected Sihamoni as the new king. Cambodia's National Assembly then decided to give Sihanouk the title of King Father, allowing him the same privileges he has as the reigning monarch, according to his website.
Sihanouk saw Cambodia go from French rule to independence, then to the brutal Khmer Rouge regime and the guerrilla war that followed its toppling. He then watched his country develop into the constitutional monarchy it is today.
He came from a royal lineage, but it was France that placed Sihanouk on the throne in 1941, according to the foreign ministry of Australia, which has played a key role in Cambodia's transition toward peace.
The king dissolved the nation's parliament in 1953, which helped bring about Cambodia's independence.
Two years later, he abdicated the throne to his father but remained active as Cambodia's prime minister. In 1960, he became the South Asian nation's head of state following his father's death.
In the 1960s, amid a region simmering with conflicts such as the Vietnam War, Cambodia soon became home to a number of North Vietnamese training camps. That prompted U.S. air strikes on those camps in 1969.
The following year, U.S.-backed Gen. Lon Nol declared a coup d'etat while the king was on an official visit to the Soviet Union and abolished the monarchy.
Sihanouk aligned with the Khmer Rouge, a growing ultra-Maoist group which sought to transform Cambodia into an agrarian utopia.
The king, forced into exile in China, led the resistance movement, while the Khmer Rouge gradually gained strength.
When the group, led by Pol Pot, won control of Cambodia in 1975, Sihanouk returned as head of state. But by the following year, he was placed under house arrest.
From 1975 to 1979, Khmer Rouge led a bloody period of mass killings, public executions and torture centers. While no one knows for certain how many people were killed by the regime, experts estimate 1.7 million fatalities -- or at least a quarter of Cambodia's population died from executions, diseases, starvation and overwork.
Sihanouk himself lost five children and 14 grandchildren at the hands of the Khmer Rouge. He was confined to the royal palace until Pol Pot was overthrown three years later. He was away from Cambodia from 1979 to 1991.
The king subsequently became president of the new republic, but it wasn't until 1993 -- when Cambodia held its first parliamentary elections -- that the king's powers were restored and Cambodia became a constitutional monarchy.
Elizabeth Becker, the author of "When the War Was Over: Cambodia and the Khmer Rouge Revolution," told CNN after the king abdicated in 2004 that Sihanouk was "larger than life" and brought both good and bad to his country.
He tried to bring Cambodia into the modern world and protect it from its neighbors, but he brought about divisions in the process, she said.
"He threw his prestige and politics behind the Khmer Rouge when they started the rebellion and it was his name that helped convince a lot of peasants to go along with the Khmer Rouge," Becker told CNN.
"Then later, after the Vietnamese invasion, he continued to help the Khmer Rouge at the United Nations with political prestige, so his is a very checkered legacy."