Police are scouring mountains for an armed military veteran after four people were killed in a shooting in a Montana bar.

Michael Paul Brown, 45, fled The Owl Bar in the town of Anaconda in a white pickup truck but later ditched it, authorities say.

The shooting happened at about 10:30 local time on Friday morning.

Residents were told to stay at home and on high alert as the manhunt continued.

Lee Johnson, of the Montana Division of Criminal Investigation, said: “While law enforcement has not received reports of Brown harming any other individuals, he is believed to be armed, and he is extremely dangerous.”

Authorities said they would release the names of the victims once all of their families have been notified.

“This is a small tight-knit community that has been harmed by the heinous actions of one individual who does not represent what this community or Montanans stand for,” Mr Johnson said.