Crewmen were warned to be on the alert for bogus mainland security officers yesterday.
The move came as Guangdong officials announced new maritime security measures.
A Guangdong Public Security Bureau spokesman said there had been cases where people had boarded vessels by posing as border defence officers.
'There was no system of enforcement at sea in the past. We are now setting up one to regulate it,' the spokesman said.
The bureau's border defence department's chief of general staff Xing Jianjiang said the new system aimed to allow fishermen and other vessel operators to identify genuine security officers more easily.
He said vessel operators or crewmen should report any suspicious cases by calling the satellite marine alarm system on 110.
