Chea Sim, president of the ruling Cambodian People's Party of Prime Minister Hun Sen and also president of the Senate, died at 3.45pm Monday, according to Yim Leang, head of his bodyguard unit.
Prior to his death, he was suffering from diabetes and other illnesses.
Following the fall of the Khmer Rouge regime in 1979, Chea Sim held various positions in both the executive and legislative branches, ranging from chairman of the Council of State, minister of interior and head of both the lower and upper house.
He served as president of the National Assembly of Cambodia from 1981 to 1998, with a short interval as vice president from June to October 1993 due to a political change and was president of the Senate from 1999 until his death.
As for the ruling party, Chea Sim served as its president since 1991 while Hun Sen serves as vice president of the CPP.
Recently, Hun Sen said if Chea Sim were to pass away, he would become president of the party.
Chea Sim was born in Svay Rieng province, located in the eastern part of Cambodia near its border with Vietnam.
Due to his poor health, Chea Sim had been absent from the Senate's sessions since last year and the Senate hearings were presided instead by his deputy Say Chhum, who is secretary-general of the CPP.
Chea Sim was awarded an honorary high title of Samdach Akeak Moha Thomak Pothisal by the late King Norodom Sihanouk in the 1990s, and from time to time he served as acting head of state when the king was absent from the country.