A shooting in US state Pennsylvania left four people dead and three injured, local TV reports said.

According to a CBS Pittsburgh, the deadly shooting took place in Frankstown Township near Altoona, western PA. Four people, including the shooter, were dead, and three state troopers were injured.

The report said the troopers were shot, but are expected to survive. The report indicated they shot and killed the suspect.

The suspect was reported to be opening fire on a rural road in the area, shooting randomly.

Blair County District Attorney Rich Consiglio was quoted by Fox TV as saying the shooting scene on Friday morning "extended over several miles", and the dead were three men and one woman.

State police say one trooper was struck by gunfire but escaped serious injury because he was wearing a bulletproof vest. A second trooper was hit by shattered glass and a third was in a crash involving the gunman.

Reports indicated the public isn't at risk. Township supervisor Mark Schroyer says nearby schools weren't placed on lockdown.

The identities of the victims and gunman weren't immediately released.