The chief of Chea Sim's bodyguard unit was quoted on Monday in the Cambodian press as saying that Sim had died after several years of ill health.

Hospitalized in recent months, Sim had also sought treatment in Vietnam for lung problems, the Phnon Penh Post newspaper reported.

Sim became a revolutionary in the 1950s and, like his ally and Cambodian Prime Minister Hun Sen, was a member of the communist Khmer Rouge when they seized power in 1975 after a civil war.

Both Sim and Sen fled the group to join a resistance faction formed by neighboring Vietnam, which installed them as Cambodia's new leaders after ousting the Khmer Rouge in 1979.

Sim was president of the ruling Cambodian People's Party since it was formed in 1991, and president of the Senate since 1999.

Sen announced in April that he would take over the presidency of the Cambodian People's Party in the event of Sim's death.

ksb/msh (AP, dpa)