Japanese police identified a record 1,559 minors aged under 18 as victims in child pornography cases in 2019, with many of them coerced or deceived into sending nude selfies, a National Police Agency report said Thursday.

The total number of victims, up 22.2 percent from a year earlier, included 584 who ended up sending nude photos or videos to suspects, 381 whose images were photographed or filmed secretly, 221 who were involved in prostitution or sexual acts, and 126 who were raped or indecently assaulted.

Most of the victims were females, totaling 1,350. Of the total, junior high school and high school students made up around 80 percent, and there were also 240 elementary school pupils and 51 preschool children.

Among the victims who were tricked into sending nude selfies, a male junior high school student sent a video of himself completely naked at the request of a man in his 20s masquerading as a female junior high school student, according to the agency.

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Separate NPA statistics released the same day showed that last year a record 2,082 minors aged under 18 were victims in criminal cases involving social networking platforms, up 271 from a year before. Most of the cases were sex-related offenses.

More than half of the victims were high school students at 1,044, an increase of 53, but there were also 72 elementary school pupils, up 17. The number of junior high school students surged 223 to 847.

"The prevalence of smartphones has led to an increase in younger victims," an agency official said.

Twitter was the social networking platform on which the largest number of victims was targeted at 807, topping the list for the fifth year in a row, followed by Himabu, a popular messaging app for students, at 307, Instagram at 120, Line at 81 and MarinChat at 70.

Instagram ranked within the top five platforms for the first time in the NPA surveys. On the site, cases typically begin with suspects commenting on photos uploaded by the victims, thereby establishing contact.

The agency said it plans to enforce online monitoring and demand that operators of social networking services take stricter measures against criminal activities by users.