Police in Derry say young people are organising street fights using the BlackBerry messaging service on their mobile phones.
At the weekend, a 28-year-old man, who police say was an innocent passerby, was beaten unconscious after teenagers had gathered in Gobnascale.
Police believe the teenagers, who were male and female, had arranged a fight via BBM.
Inspector Bill Mulligan said this type of behaviour could have tragic consequences.
