US authorities in the northwest Washington state are searching for a gunman 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, Washington State Patrol spokesman Mark Francis tweeted at about 1.00pm (AEST).

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.

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.

– with Reuters