Washington, Nov 2 (IANS): At least three people were killed when a gunman opened fire on a crowd inside a Walmart store in the US state of Colorado, the police said.

The attack took place on Wednesday evening in the suburban Denver store and the gunman was still at large, the New York Times reported.

The police released a photograph of a middle-aged white man in a black jacket leaving the Walmart in the city of Thornton.

"It's random as of right now," said a Thornton Police Department spokesman. "The person came in and just shot towards a group."

The spokesman said said that investigators did not know of a motive and said the suspect did not speak before opening fire with a handgun inside the store's south entrance.

Two men were pronounced dead at the scene and a woman later died at a hospital. The police did not find the weapon.

The incident came after Sayfullo Habibullaevic Saipov on Tuesday drove a pickup truck down a busy bike path in New York's Lower Manhattan area, killing eight and injuring 13. He was shot by police and then hospitalised.

US federal prosecutors have filed terrorism charges against Saipov.