A shooter opened fire on a psychiatric hospital in the northeastern US state of New Hampshire on Friday, killing one person before being fatally shot by police, authorities said.

The suspect entered the New Hampshire Hospital in Concord and shot one person in the lobby, state police Colonel Mark Hall said.

"A state trooper assigned to the hospital and in close proximity immediately engaged, shot and killed the suspect," he told a news conference, adding that the attack was confined to the hospital lobby.

Hall did not identify the shooter or the victim.

"There is no threat to the public, and there was no threat to the patients or staff at the hospital," he said.

New Hampshire Hospital in the state capital Concord is a 185-bed inpatient facility that treats patients with acute mental illness.

Shootings are alarmingly common in the United States, a country where there are more guns than people and where attempts to clamp down on their spread are always met with stiff resistance.