Children are "strangling" themselves to get high and then sharing the videos on the Internet, campaign groups have warned.

Nicknamed "Space Monkey," the practice involves squeezing the carotid arteries in the neck to restrict the flow of blood to the head. Releasing the pressure leads to a sudden rush of oxygen to the brain, giving a feeling of euphoria.

But it can lead to brain damage, unconsciousness and death. The craze is well known in the U.S., Britain and France.

The U.S. Center for Disease Control and Prevention claims in the last 10 years 86 children may have died in the U.S. playing "the choking game."

YouTube videos seen by Sky News show youths taking it in turns to squeeze each others necks before appearing to lose consciousness. In one video, a teenager is seen hyperventilating before having his arteries crushed — and then passing out.

On a Yahoo forum, 'Baay', writes: "Just as I passed out, I said, 'It's so scary.'"

"Then I fainted and I started like having a fit or something like shaking, was it a fit? And my eyes were open and rolling back. Now everyone is doing it at school, and apparently if I was doing all this I could of died, is that true?"

Teenagers are also sharing instructional videos to show others how it's done and using scarves and ropes to choke themselves. Others are posting Space Monkey reports online.

"First you get asphyxia anoxia which is a lack of oxygen to the brain, then you get a sudden rush of oxygen to the brain," said Professor Steve Field, chairman of the Royal College of General Practitioners. "Children are copying what they see in the videos and think they'll get a similar high to taking drugs."

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