Two people are dead and three others injured after a terrifying mass shooting at a campground that was hosting a popular music festival in the US’s Washington state.

Police said the gunman began firing into the camping area of the Beyond Wonderland electronic music festival.

After the initial shots, the suspect started moving through the site and “continued to shoot randomly into the crowd”, said Kyle Foreman, public information officer with the Grant County Sheriff’s Office.

He was eventually confronted by police and taken into custody.

A public alert had advised festivalgoers that there was an active shooter in the area and to “run, hide or fight”.

But Mr Foreman said there was no effort to evacuate the festival.

The festival continued following the shooting and did not end until early Sunday morning (local time), he said.

“He was, again, on the periphery of the property. Law enforcement had eyes on him, and they were able to keep him in that area. He wasn’t moving toward the venue,” Mr Foreman said.

The suspect was among those injured. He was shot in the confrontation with law enforcement.

Tweet from @BeyondWlandPNW

Authorities received the first report of the shooting shortly before 8.30pm on Saturday (local time) not far from the Gorge Amphitheatre, where thousands of people were attending the festival.

The Gorge is near the small city of George, about 240 kilometres east of Seattle.

The suspect was hospitalised for his injuries, but no further details were immediately released. Details on the victims would be released at a later time, Foreman said.

Organisers of the Beyond Wonderland electronic music festival said on social media that Sunday’s events at the Gorge were cancelled.

Concert organisers described the shooting site as an “overflow camping area,” and most people who were staying there were likely at the concert when the shooting occurred, Mr Foreman said.

An independent oversight group, the North Central Washington Special Investigation Unit, is investigating the shooting.