A suspect is on the run after four people were killed in a shooting at a bar in the US state of Montana, authorities say.

The shooting happened at The Owl Bar in the city of Anaconda at around 10:30 local time, the Montana Division of Criminal Investigation confirmed to the BBC's US partner CBS.

The US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) said it was "responding to a shooting where multiple parties have been shot at a business in Anaconda".

Anaconda is a former copper smelting hub, with a population of almost 10,000 people in southwestern Montana, 109 miles (175km) west of Bozeman.

The Anaconda-Deer Lodge County Law Enforcement Center named the suspect as Michael Paul Brown in a social media post, adding he is "believed to be armed and dangerous".

"If seen do not approach," the department said. "Contact 911 for any way to contact Michael Paul Brown."

Officials are calling on Anaconda residents to stay home and lock their doors.

The Granite County Sheriff's Office, which is nearby to Anaconda, posted on social media that the gunman "is said to be wearing a tye dyed shirt, blue jeans and a orange bandana".

The sheriff's office added that the gunman's home in Anaconda had been searched, and "cleared by SWAT" teams.

Montana Governor Greg Gianforte said he was monitoring the response to the incident.

"Please join Susan and me in praying for the victims, their loved ones, and the brave law enforcement officers responding to this tragedy," the governor said on social media referring to his wife, Susan Gianforte.

The FBI was also at the scene and is helping in the investigation.

Montana Senator Steve Daines told local media that the "massive manhunt" is being aided by police drones.

The Owl Bar was built in 1893 to serve Anaconda's copper workers, according to a 1987 article in the Montana Standard newspaper. It's located in a neighbourhood of Anaconda called Goosetown. (BBC, but headline rejigged)