Three students have been robbed at knifepoint of their mobile phones while playing Pokemon Go.
The individuals were targeted in Hulme, Manchester, on Friday night just hours after Greater Manchester Police (GMP) warned of the dangers of using the phone app.
The force had said it was concerned that the app could provide another online avenue for criminals to exploit.
Its advice to users included paying attention to your surroundings, especially in built-up areas.
The robberies took place in Hulme Park at about 8pm, added police.
The augmented reality game was launched in the UK on Thursday and has exploded in popularity. It uses the phone's GPS location data to allow players to roam the real world and catch virtual monsters.
GMP's public protection division also urged parents and teachers to speak to young people about staying safe when using the app.
Detective Superintendent Joanne Rawlinson said: "We know that criminals move quickly to exploit the latest developments to target victims and Pokemon Go will already be in their sights.
"There have already been incidents in America where young people are thought to have been targeted through the app.
"I would urge parents to speak to their children about the app and the best ways to make sure they stay safe. Talking to your child is one of the best ways to keep them safe."