A US sailor fatally shot two people and wounded a third at the Pearl Harbor Naval Shipyard in Hawaii on Wednesday before committing suicide, an official said.

The two people killed were Department of Defense civilian employees, while a third civilian was wounded but "in stable condition at (an) area hospital," the official told AFP.

Earlier, a spokesman for the US base would only say that security forces had responded to reports of a shooting at around 2:30pm local time and that the base was on lockdown for several hours.

One witness told local media he was sitting at his computer when he heard shots fired and saw three victims on the ground.

The witness, who did not want to be identified, said he then saw the gunman who was wearing what appeared to be a navy or sailor's uniform shoot himself in the head.

Hawaii News Now said several civilians were among the gunshot victims.

The shooting reportedly took place near the south entrance to the sprawling base.