BEIJING, Feb. 24 -- Chinese authorities have vowed to deter judicial corruption in commutation of sentences and probation following a string of convicts who bribed their way out of prisons.

"Terms and procedures on commutation, parole and serving a sentence outside jail for medical reasons should be stringent within the frame of the law," said an instructive document released Monday by the Commission for Political and Legal Affairs of the Communist Party of China (CPC) Central Committee.

In a high-profile case, Zhang Hai, former board chairman of Jianlibao Group Co. Ltd., a Chinese beverage giant based in south China's Guangdong Province, fabricated evidences to have his sentence reduced by 5 years in a second court trial and had his jail term further reduced by more than four years while he was serving.

Police officers, prison and court officials were involved in Zhang's lessened sentence and commutation. Zhang escaped overseas after he was freed.