Police in Christchurch expect there are more victims of a man who posed as a woman to extort sexual favours from young males

Oliver Kiesanowski has been jailed for five years, after obtaining explicit images from victims and using them to blackmail them send more.

Police say there are eight identified victims of the sextortion, while nine remain unidentified.

They believe there could be more, and are encouraging anyone who hasn't yet contacted Police, to make a report.