Police arrested six children for allegedly using a social networking website to organise gang fights.
Detectives acted on intelligence that youngsters used internet site Bebo to arrange a series of confrontations involving rival groups across Derby between November and January, Derbyshire Police said today.
The detained youths, aged 14 and 15, were questioned by officers this week about the fights and their postings on the web, the force said.
They have been released on police bail, but five will face final warnings and be made to sign acceptable behaviour contracts, said a force spokesman.
The spokesman said: "We have taken what we think is early preventative action before it gets serious.
"Some people think the internet is private but it's a public place and if they are posting messages which could lead to disorder then that's something we will take a keen interest in."
No one was seriously injured in the incidents but police warned parents to be aware of what their children are looking at on their computers.
Bebo has agreed to take the material relating to the fights in Derby off its site.