SHANGHAI (REUTERS) - China's top anti-corruption watchdog has tightened supervision of its 500,000-plus corruption investigators, after some of its own staff were caught in graft probes.

The Central Commission for Discipline Inspection (CCDI) said in a statement on its website late on Sunday (Jan 8) that a new regulation would be applied to procedures such as evidence collection and case reviews, without providing further details.

"Trust cannot replace supervision," the CCDI said in the statement, released after it held an annual three-day meeting. "We must make sure the power granted by the (Communist) Party and the people is not abused," it said.

State newspaper the China Daily, which did not indicate its sources, said the new regulation would set clear standards on how to handle corruption tips, how to handle ill-gotten assets, and would encourage audio and video recordings to be made throughout interrogations.

More than 7,900 disciplinary officials have been punished for wrongdoing since 2012, the newspaper said, citing CCDI figures. Of those, 17 were CCDI staffers who were put under investigation for graft, it said.

On Friday, state news agency Xinhua quoted Chinese President Xi Jinping as saying that the battle against corruption "must go deeper", and called for the Communist Party to be governed "systematically, creatively and efficiently".