John Demers, chief of the US Justice Department's National Security Division, told the Aspen Institute think tank on Wednesday the researchers had left the country while the department launched multiple criminal cases against Chinese operatives for industrial and technological espionage.

A Justice Department official said they were a different group to those mentioned by the State Department in September

At that time, the department said the United States had revoked visas for more than 1000 Chinese nationals under a presidential measure denying entry to students and researchers deemed security risks.

The official said the researchers Demers referred to, who US authorities believed were affiliated with China's People's Liberation Army, fled the United States after the FBI conducted interviews in more than 20 cities and the State Department closed China's Houston consulate in July.

"Only the Chinese have the resources and ability and will" to engage in the breadth of foreign influence activity that US agencies have seen in recent years, Demers said.

William Evanina, chief of counterintelligence at the US Director of National Intelligence, told the same event Chinese agents were already targeting personnel of the incoming Biden administration, as well as "people close" to Biden's team.

Evanina said Chinese researchers in the United States who were under scrutiny of US agencies were "all coming here at the behest of the Chinese government".

China described the visa crackdown earlier this year as "naked" political persecution and racial discrimination that seriously violated human rights.

Sino-US relations have deteriorated to their worst in decades during outgoing President Donald Trump's tenure with disputes simmering over issues from trade and technology to Hong Kong and the coronavirus.

Australian Associated Press