FBI Director Christopher Wray has warned that Chinese hackers are preparing to target US infrastructure to cause significant disruption to American citizens.

Wray spoke before a House committee on China on Wednesday.

He said, "China's hackers are positioning on American infrastructure in preparation to wreak havoc and cause real-world harm to American citizens and communities, if and when China decides the time has come to strike."

He said there has been far too little public focus on their efforts to target vital systems, such as water treatment plants and the electric grid.

Separately on Wednesday, the US Justice Department said in a statement that officials disrupted an effort by a hacking group backed by the Chinese government.

The department said the hackers tried to utilize malware-infected privately-owned routers in home offices and small businesses to conceal the origin of further hacking activities. These attempts included a campaign targeting critical infrastructure organizations in the US.

US Attorney General Merrick Garland said in the statement, "The United States will continue to dismantle malicious cyber operations that undermine the security of the American people."