Police are responding to a reported shooting at a high school north of Seattle.

A spokeswoman for the Washington State Patrol confirmed reports of an ongoing incident at Marysville-Pilchuck High School in Washington state.

The school is on lockdown "due to an emergency situation," the school district said in a statement.

An eyewitness reported that at 10.30am US time, a student walked into the cafeteria, went to a table, pulled out a gun and shot 4-6 students who were sitting there. Marysville Police Department says they received a 911 call from "somebody on campus" about the shooting as it was happening.

There are unconfirmed reports that between two and six people have been injured after gunfire was heard in the cafeteria.

Two victims of the shooting have reportedly been airlifted from the school. One of the victims has sustained an injury to the head. The victims were admitted to Providence Regional Hospital in nearby Everett. Three victims of the shooter are reportedly in critical condition and undergoing surgery.

An eye-witness told news channel KIRO7 that the gunman is among the dead, as a result of a self-inflicted wound. Police have confirmed that the shooter was a student.

Students have reported pandemonium in the cafeteria after the shooting, with dozens rushing for doors and then jumping a fence to escape.

One pupil has told local media every exit was jammed with kids escaping gunfire. "I heard 3 gunshots and I ran," he added.

TV footage shows students being evacuated from the building with their arms raised, while armed police conduct searches with guns drawn.

Students from the school have apparently been calling police from hiding spots inside school rooms. There are about 2,500 pupils at the school.

Police cars and ambulances are assembled outside the school.

An FBI spokesperson in Seattle, Ayn Dietrich, said the agency had sent personnel to the scene.