WINNIPEG -- The Canadian Centre for Child Protection says it is seeing an alarming increase in the number of teens who are sharing sexual images of themselves through live web chats and then being extorted for money.

The centre, based in Winnipeg, said its tipline has received more than a dozen calls from teens in the past few weeks saying they are being blackmailed this way.

Signy Arnason, the centre's associate director, said an adult poses as a teenager and secretly records teens exposing themselves. The adult then threatens to share the sexual images unless the teen pays between $200 to $900.

"The number 1 request from these kids is 'I just want this to go away, I don't want my parents to know'," Arnason said. "It's 'Help me, help me make this issue go away."'

This kind of "sextortion" has been blamed for driving some tormented teens to commit suicide.

Amanda Todd, a 15-year-old in British Columbia, committed suicide in 2012 after being extorted for two years. She exposed herself while on a web chat and the image was used to blackmail her into putting on another "show" online. She eventually posted a heartbreaking, nine-minute video online detailing her torment before committing suicide.

The suicide of another sexually exploited teenager in Nova Scotia in 2013, who cannot be named under a publication ban, turned a spotlight on cyberbullying and prompted new laws on the distribution of sexual images.

But Arnason said this kind of continued sexual extortion highlights the risks teens face with live video streaming because they can be filmed without their knowledge. She said teenagers are impulsive and sexually curious -- a deadly combination online.

"When they're on live video chat, they're really not thinking about the tactics somebody could be using on the other side to be recording what they're doing," she said. "They think they're living in the here and now -- it's live -- and when they close that off, it's over."

Even if the blackmailer is paid, Arnason said that is no guarantee the incriminating pictures or video are destroyed. Often the extortion escalates, she said.

"The individual still has that video or image," she said. "They can tell you they're deleting it but why would anybody believe them? They're still in possession of what these kids so desperately want back."

Although there is more awareness about cyberbullying, Arnason said parents must talk to their children to make sure they understand the dangers of sexual behaviour online. Parents also have to make sure their teens feel comfortable coming to them if they run into trouble online, she said.

"It doesn't mean you're not going to be upset or that you don't need to talk about it the next day but you need to let your kid know you're there for them," Arnason said.

"If we can increase the likelihood that they come forward, we're going to reduce the chances that they pay the money, that they maybe send another sexual image hoping it will go away."