Cambodia Deputy Prime Minister Sok An, left, with Cambodian Prime Minister Hun Sen in 2013. (Heng Sinith/Associated Press)

Sok An, a deputy prime minister of Cambodia who was one of Prime Minister Hun Sen’s closest political and personal allies, died March 15 at a hospital in Beijing. He was 66.

A government statement confirmed the death but did not provide the cause. Sok An had been absent from public life for several months while he was widely understood to be undergoing medical treatment. He suffered from diabetes and other ailments.

Sok An was trusted with the sensitive task of negotiating with the United Nations to hold an internationally assisted tribunal to try leaders of the Khmer Rouge for genocide and other crimes, and overseeing Cambodia’s role in it.

Cambodia, by holding the trials, sought to placate Western aid donors essential to its economy while limiting any domestic fallout, because Hun Sen and some of his political allies had at one time belonged to the Khmer Rouge. Trials began in 2009 but so far have led to the convictions of just three defendants.

Sok An’s closeness to Hun Sen was underlined by the marriage of one of his sons, Sok Puthyvuth, to one of the prime minister’s daughters, Hun Mali. Another son, Sok Soken, is married to the daughter of Industry Minister Cham Prasidh, and late last year was appointed an undersecretary of state at the Ministry of Foreign Affairs. Hun Sen has served as Cambodia’s leader since 1985.

On Monday, King Norodom Sihamoni granted Sok An the relatively exclusive royal title of “samdech” — loosely translated as “lord” — for “protecting democracy, building up national peace and ensuring social stability.”

Hun Sen and his wife, Bun Rany, and other senior ruling party members also hold the honorific title. The bestowal of the title, presumably at Hun Sen’s request, came as rumors circulated that Sok An was near death.

In 1990, Sok An became vice minister of foreign affairs and vice minister of the interior. He was appointed to the Central Committee of Hun Sen’s ruling Cambodian People’s Party in 1992, and became deputy prime minister in 1998.

Unlike other senior members of the Cambodian People’s Party, Sok An never was seen as a possible political challenger to Hun Sen, playing more the role of an apparatchik.

Posts he held included chairman of the Council for Demobilization of Armed Forces, chairman of the National Tourism Authority of Cambodia, chairman of the Council for Public Administrative Reform, chairman of the Cambodian National Petroleum Authority and vice chairman of the National Information Communication Technology Development Authority.

— Associated Press