China's Bureau of Surveying and Mapping (BSM) has warned foreigners to turn off the GPS functions on their mobile phones, or risk arrest.
The bureau warned foreigners using GPS devices on mainland China that they could be detained if suspected of conducting illegal mapping.
The bureau has launched a crackdown on "illegal surveying", the South China Morning Post reported, with foreigners the main targets.
Under Chinese law, non-Chinese institutions or individuals intending to use mapping devices in China must file a request to the government - which can take months to approve - have their data submitted for vetting and be 'assisted' by Chinese authorities.
A US citizen, mining expert Calvin Herron, was arrested for using a handheld GPS device in a village near Luoyang in 2007, the bureau said. He was detained for four months, then deported and fined 100,000 yuan ($14,640).
Chinese experts believe Herron was arrested for getting too close to guided missile sites believed to be situated in Luoyang.