One state trooper was injured and the gunman was killed in a shooting at a bus station in the US state of Virginia.

Six people were harmed in the attack which took place at Richmond's Greyhound Station at 2.45pm local time on Thursday.

Police were holding a training exercise when the suspect approached and shot one of the troopers in the chest, NBC News said.

The troopers then returned fire and killed the gunman.

Pictures showed ambulances and large numbers of police at the scene.