A picture that has spread online of an advertisement for Chinese to ask foreigners to call the police on their behalf in Hefei, Anhui province, has caught the attention of the police.

"Police will pay more attention if the person who reports a case is a foreigner so there will be a higher detection rate," reads the advertisement posted online.

A spokesman for the Hefei police, surnamed Cheng, told China Daily on Monday, "We cannot locate where the picture was taken from the information on the Internet, and the authenticity of the advertisement is doubtful."

Police said the procedure for processing a case after receiving a report is the same no matter where the complainant is from.

Some individual cases, in which the victims were foreigners, were solved within a relatively shorter time mainly because of pressure from media reports, police said.