Pol Pot, the controversial Khmer Rouge leader, has been replaced as premier of the radical Communist government fighting for control of Cambodia, diplomatic sources said yesterday.

They said that the pro-Peking Communists, who were ousted last January by a Vietnamese-led invasion, replaced Pol Pot by the more moderate Khieu Samphan in an effort to improve their international image.

Pol Pot, 51 was given no Cabinet post in the shakeup but continued as supreme commander of Khmer Rouge forces. Khieu Samphan, 48, retained his titles as president and chief of state.

The shakeup occurred Dec. 17 at a meeting of 67 high-ranking Khmer Rouge officials at a secret base in Cambodia's Cardamon Mountains, according to intelligence reports.

Khieu Samphan, a Marxist economist, has escaped much of the criticism leveled at Pol Pot for the barbarism and massacres committed during the Khmer Rouge reign. Thai sources said his appointment as premier was "a natural effort to find a person who can be accepted by all Khmers."

Khmer Rouge leaders also scrapped their 1975 Socialist constitution in an apparent effort to open the way for cooperation with other Cambodian resistance forces fighting the Vietnamese.

Several anti-Vietnamese resistance groups are said to operate inside Cambodia but they had refused to cooperate with Pol Pot.