Japan's police agency reported yesterday that the number of violent crimes linked to online dating sites had almost doubled in the first half of this year from the same period last year.

　　Cases involving violent crimes, including homicide, assault, robbery and rape, rose by 1.9 times to 63 incidents from 34, according to a report released yesterday by the National Police Agency.

　　In particular, robberies more than tripled to 19 from 6.

　　The majority involved ploys luring men with promises of companionship, then stealing their money and valuables, a police spokesman said.

　　The overall number of incidents, which involved anything from indecent exposure to offering minors cigarettes to child prostitution, dropped slightly to 781 from 793.

　　However, 80 percent of the victims were girls under 18, according to the spokesman.

　　In recent years, the spread of the Internet has led to a rise in teenage prostitution, police have said.

　　An estimated 5 percent of girls in Tokyo's middle and high schools have turned tricks insgroupsto buy the latest fashions, according to a December police report.

　　The problem has sparked concern among authorities, who have pushed for greater restrictions.

　　The restrictions would include a law that would make it illegal for dating sites to be accessed by minors.

　　In yesterday's report, the number of cases involving sex with minors was down by 74 incidents, or 18.5 percent, to 326.