The number of fake marriage cases involving foreigners surged to 153 last year, up 14.2 percent, the National Police Agency said Thursday.
The police took action, such as questioning, arresting and sending cases to prosecutors, against 471 people, up 25.6 percent.
They will keep a closer eye on sham marriage cases because they lead to a host of other crimes, the NPA said.
Some foreigners get involved in crimes after obtaining resident alien status following bogus marriages to Japanese, while some organized crime groups obtain funds by arranging the marriages, it said.
Meanwhile, the number of cases involving violations of the criminal code and other punitive laws by foreigners totaled 19,820, down 28.8 percent, with police taking action against 11,866 people, down 10.5 percent.
Of these, the number of thefts fell 47.5 percent. The NPA believes that enhanced surveillance of automobile dismantling facilities that are believed to function as headquarters of foreign theft groups contributed to the decline.