A military veteran accused of killing four people in a bar shooting in the US state of Montana last week has been arrested, according to officials.

Michael Paul Brown, a US Army veteran, is accused of opening fire inside the Owl Bar in the city of Anaconda on 1 August.

Local, state and federal authorities launched a manhunt, finding the suspect fled to the nearby foothills and shed his clothing after the attack at the pub, where he was reportedly a regular.

No motive for the attack has been released.

"I am proud of the unrelenting law enforcement effort this week to find and arrest Michael Paul Brown," Montana Attorney General Austin Knudsen said, announcing the arrest.