A police chief in Northeast China is under investigation over claims he promoted twin sisters he was having an affair with.

Qi Fang, director of public security for the Xinjiang Uygur autonomous region's Usu county, is being investigated by the Party anti-graft agency.

"The Party discipline committee has decided to investigate, but our bureau cannot give any information at this stage," a discipline official at the Usu public security bureau said on Thursday morning.

According to Beijing News, which quoted an unnamed online source, Qi is accused of giving his two mistresses posts and using public funds to rent an apartment for them in an exclusive community.

One woman was appointed deputy director of the county's special police force in March, while the other joined its traffic police operations, the report said.

The women, 31, are former actresses, the online source said.

The Beijing News also quoted a deputy Usu police chief surnamed Yang who said the official had not been dismissed.

A policewoman in the county's traffic police division said the two women mentioned, aged 28 and 26, are sisters but not twins, the report said.