UPDATED 10.08AM A man ploughed his car into a group of pedestrians at Ohio State University and then got out and began stabbing people with a butcher knife before he was shot to death by an officer, campus police say.

On Monday morning nine people were hurt, one critically, and Columbus Police Chief Kim Jacobs said police were looking into whether it was a terrorist attack. The FBI and other agencies joined the investigation.

The details emerged after a morning of confusion and conflicting reports that began with the university issuing a series of tweets warning students that there was an "active shooter" on campus near the engineering building and that they should "run, hide, fight".

Numerous police vehicles and ambulances converged on the 60,000-student campus, and authorities blocked off roads.

Ohio State Police Chief Craig Stone said that the attacker drove over a curb outside a classroom building and that an officer who was nearby because of a gas leak shot the driver in less than a minute.

Angshuman Kapil, a graduate student, was outside the building when the car barreled onto the sidewalk.

"It just hit everybody who was in front," he said. "After that everybody was shouting, 'Run! Run! Run!"'

The shelter-in-place warning was lifted about an hour and half later and the campus was declared secure after police concluded there was no second attacker, as rumoured.

At least two people were being treated for stab wounds, four were injured by the car and two others were being treated for cuts, university officials said.

Classes were cancelled for the rest of the day.