SWAT teams and police respond to reports of a shooting on campus at Ohio State University, Monday, Nov 28, 2016, in Columbus, Ohio. [Photo/IC]

Of the 11 people injured, one was in critical condition.

A series of tweets by the university warned that there was an "active shooter" on campus and that students should "run, hide, fight". The warning was prompted by what turned out to be police gunfire.

The initial tweet from Ohio State emergency officials went out around 10 am and said: "Buckeye Alert: Active Shooter on campus. Run Hide Fight. Watts Hall. 19th and College." University President Michael Drake said the warning was issued after shots were heard on campus.

Ohio State Police Chief Craig Stone said that the assailant deliberately drove his small gray Honda over a curb outside an engineering classroom building and then began knifing people. A campus officer who happened to be nearby because of a gas leak arrived on the scene and shot the driver in less than a minute, Stone said.

"This was done on purpose," Stone said of the attack.

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

"It just hit everybody who was in front," he said.

Student Martin Schneider said he heard the car's engine revving.

Surveillance photos showed Artan in the car by himself just before the attack, but investigators are looking into whether anyone else was involved, the campus police chief said.

"I thought it was an accident initially until I saw the guy come out with a knife," Schneider said, adding that the man didn't say anything when he got out.

Most of the injured were hurt by the car, and at least two were stabbed, officials said. One had a fractured skull.

Asked at a news conference whether authorities were considering the possibility it was a terrorist act, Columbus Police Chief Kim Jacobs said: "I think we have to consider that it is."

The bloodshed came as students were returning to classes following the Thanksgiving break and Ohio State's football victory over rival Michigan that brought more than 100,000 fans to the campus on Saturday.