The number of crimes linked with Internet dating sites has more than tripled in the first half of this year compared with all of last year, according to a National Police Agency report released Thursday.

There were 302 cases from January through June, but only 104 for all of 2000, the report says.

The number of crimes involving child pornography and sex with minors surged from 41 cases last year to 133 in the first half of this year, the report says.

A rise in the number of serious crimes, including murder and rape, was also seen.

Murders have jumped to five from one last year and the number of rapes has already hit 20, compared with eight in 2000, the report shows.

In the majority of cases, the victims were women and minors.

The NPA has instructed police departments nationwide to make stronger efforts to warn parents and teachers that such crimes are proliferating.

Of the 302 cases, 133 involved the purchase of sex from minors and 59 involved violations of ordinances designed to protect them, the report says.

The cases involved 283 victims, of which 265, or 94 percent, are women, according to the report.

Of the victims, 218, or 77 percent, were below the age of 20, and 215 of them were girls.

Mobile phones are also becoming a more popular way of accessing the sites. About 85 percent of the hits were made by mobile phones in the first half of this year, compared with 57 percent last year, the report says.