China's top judge has said the ruling Communist Party's decision to investigate former senior leader Zhou Yongkang demonstrates clearly that no party member is above the law, the semiofficial China News Service reported.

The investigation "fully illustrates that in socialist China, no power exists outside the cage of the system, and party members will never be allowed outside party discipline and national laws," Zhou Qiang, president of the Supreme People's Court, was quoted as saying on Tuesday.

The party announced on July 29 that it had launched a corruption investigation into former domestic security chief Zhou Yongkang, who was one of China's most influential politicians of the past decade and stood on the elite Politburo Standing Committee.

Zhou Yongkang, 71, is by far the highest-profile figure caught up in President Xi Jinping's sweeping crackdown on corruption and the most senior Chinese official to be ensnared in a graft scandal since the party swept to power in 1949.

"Leading cadres, irrespective of position or party standing and tenure, will be subject to party discipline constraints and must receive education and supervision of party organizations," Zhou Qiang said at a court meeting on party building. Zhou Qiang and Zhou Yongkang are not related.

Zhou Qiang said that, within China's court system, "the situation is grim and the tasks arduous" in the fight against corruption and for clean government.

Party leaders have said endemic corruption is a threat to party rule.