Some teenage girls are now pimping their peers through smartphone messaging applications, a youth welfare association revealed as it warned teenagers of the risks of "compensated dating" over the festive season. In one of the Federation of Youth Groups cases, a 16-year-old girl was found to have used mobile messaging apps to arrange for three girls, aged between 14 and 16, to provide men with sexual services. As a means of control over the girls, their mobile phones would be confiscated from them before they met the men. Each girl would get HK$500 of the HK$1,500 the clients were charged for a two-hour session. "The prevalence of such apps makes providing sexual services possible without any organised group," Hsu Siu-man, a supervisor at the association's Youth Wellness Centre, said, adding that such apps offered their users greater confidentiality, making it harder to track girls at risk. The association saw almost 1,300 cases of teenage sexual problems between April and September - a 13 per cent rise from last year's figure of 1,135 in the same period. Cases involving sex with girls aged under 16 saw a 45 per cent jump from the same period last year to 29 cases. Cases involving unsafe sex jumped 62 per cent to 307 cases. Online posts explicitly recruiting sex partners or seeking venues for sex parties have appeared on social media as Christmas approaches. Some of the parties involved drugs and group sex, Cecilia Ng Kam-kuen, of the association's Media Counselling Centre, said. The association warned party-goers to be wary of drugged drinks and about the criminal penalties for non-consensual sex and sex with underage girls.