Police in northwest Washington state searched for a gunman on Saturday who opened fire in a shopping mall, killing five people, according to media reports and the state's police force.

A man walked into the Cascade Mall in Burlington, Washington, about 105 km north of Seattle and began shooting at about 7 p.m. local time on Friday, Washington State Patrol spokesman Mark Francis said on Twitter.

Four women were killed in the attack in the mall's Macy's store cosmetics department, Francis told the New York Times. A man who was taken to a local hospital with serious injuries died overnight, Francis said in a statement early on Saturday morning.

Local and state police officials were not immediately available for comment but were expected to hold a news conference later on Saturday morning.

Francis said on Twitter that police and rescue workers carefully worked their way through the mall, clearing stores and evacuating shoppers, some of whom, according to local media, locked themselves in dressing rooms.

He also said police were searching the area for the shooter, who was described as a "Hispanic male wearing gray" and was last seen walking toward a nearby highway away from the mall.

Local authorities searched throughout the night for the gunman, believed to be armed with a rifle, and warned residents to remain inside.

"Tragedy has struck in Washington tonight. Our hearts are in Burlington," Governor Jay Inslee said on Twitter.

The shooting comes less than a week after a man stabbed nine people at a mall in central Minnesota before being shot dead. The FBI is investigating that attack as a potential act of terrorism.

"At this time, the FBI has no information to suggest additional attacks planned in WA state," the Washington State Patrol said on Twitter.-Reuters