A police officer is among “multiple” people who have died after a shooting at a Colorado supermarket.

Boulder police commander Kerry Yamaguchi said a suspect has been detained after the incident at the King Soopers store in Boulder on Monday.

Police said 10 people were dead, including one police officer.

Officers were seen escorting a shirtless man with blood running down his leg out of the store in handcuffs but authorities would not say if that was the suspect.

Mr Yamaguchi said police were still investigating and did not have details on a motive for the shooting at the store in Boulder, which is about 25 miles northwest of Denver and home to the University of Colorado.

Dean Schiller told The Associated Press that he had just left the supermarket when he heard gunshots and saw three people lying face down, two in the car park and one near the doorway.

He said he “couldn’t tell if they were breathing”.

Video posted on YouTube showed one person on the floor inside the store and two more outside on the ground. What sounds like two gunshots are also heard at the beginning of the video.

Law enforcement vehicles and officers massed outside the store, including Swat teams, and at least three helicopters landed on the roof.

At one point, authorities said over a loudspeaker that the building was surrounded and that “you need to surrender”.

Colorado Governor Jared Polis tweeted a statement that his “heart is breaking as we watch this unspeakable event unfold in our Boulder community”.