Teens brutally mugged after school formal

A teenager has been pistol-whipped and another stabbed in the back during a terrifying mugging in Brisbane.

It is understood the boys had been at their school formal, and possibly an after-party, before they were attacked.

The victims, both 17, were attacked from behind by two men, who also robbed them as they walked through suburban Greenslopes around midnight.

Another teen who was with the two victims was able to run away and wasn't hurt.

Police believe the offenders may have escaped in a blue sedan, which was spotted by a patrol car a couple hundred metres from the crime scene.

But the patrol car lost sight of the sedan before it was flagged down by the injured teens.

The boys were taken to hospital but their injuries are not life-threatening.

The offenders remain on the run.