A serial sex offender who was the first to be caught through a global police operation to tackle internet paedophiles was jailed for nine years yesterday.

Lee Costi, 21, was captured after an investigation by the Virtual Global Taskforce (VGT), a partnership of international law enforcement agencies established to target child abuse on the web.

Costi, a media student, targeted chatrooms used by teenagers before encouraging girls to meet for sex. He had already slept with two young girls when a third potential victim told her mother, who immediately reported him.

Grace Hale, prosecuting, told Nottingham Crown Court that the 14-year-old initially agreed to the encounter after just two exchanges with Costi on the website teenspot.com.

He made it clear he wanted to have sex with her and they arranged to meet at Nottingham train station in February but the girl became nervous and told her mother.

She e-mailed the VGT, a partnership of police from Britain, the United States, Australia and Canada.

When police seized Costi's computer they found 355 logs of sexually explicit online conversations with paedophiles from across the world. Two offenders, one in America and one in Poland, are due to be arrested.

There were also logs of conversations with young girls. Police traced two, aged 14 and 13, who had sex with him in a hotel room in Swindon,

Wilts, and in an alleyway near London's Waterloo station. Yesterday he admitted three counts of sex with children, three of internet child grooming, five of making indecent images of children, and one of possessing 43 indecent images.

Judge Jonathan Teare told Costi, from Hazelmere, Surrey: "You have developed a totally unhealthy, depraved, intense longing for younger girls. I have seen the images on your computer which clearly show a brutal, depraved interest in young girls.

"You started by chatting to young girls in chatrooms and you then groomed them. I take the view that you are a predatory paedophile.

"It must be made utterly clear to all people who meet, groom, and have sex with the young that they will be severely punished."

Jim Warnock, head of operations at the Child Exploitation and Online Protection Centre, the British arm of VGT, said: "This should send a loud and clear message to any paedophile. We are watching you and will not hesitate to move swiftly against you."