Stop pressurising expats, US warns China

US diplomats have warned China to stop using covert law enforcement agents on US soil to pressure Chinese citizens into returning home to face justice, often on corruption charges, US officials said.

Placing a law enforcement official here without notifying American authorities is criminal, CNN quoted the officials as saying.

They acknowledged the US and China have a legal cooperation treaty but stressed that it requires Beijing to share evidence and work through the US legal system.

China responded on Monday through its state news agency, Xinhua, saying it was simply fighting corruption with a programme called Fox Hunt 2015.

"China's operation is legitimate and has been approved in bilateral agreements reached earlier this year," China said. " 'Fox Hunt 2015,' which targets corrupt officials of government departments and state-owned enterprises, is an important effort of China to crack down (on) corruption."

Xinhua said US Homeland Security Secretary Jeh Johnson promised to actively support China's "Sky Net" and "Fox Hunt" operations, which aim to bring back corrupt officials.

China apparently issued its statement in response to stories in The New York Times and Wall Street Journal about the US warning.

State Department spokesman John Kirby addressed the issue in general terms on Monday at a press briefing, saying it's a criminal offence for "an individual other than a diplomatic or consular officer or attache to act in the US as a law enforcement agent of a foreign power" without notifying the US attorney general.