CHICAGO (AFP) - A malfunction in an amusement ride at the Ohio State Fair sent riders catapulting through the air Wednesday (July 26), killing one and injuring seven, US media reported.

Ohio Governor John Kasich said at a news conference on Wednesday night that "this is the worst tragedy in the history of the fair" and ordered all the fair rides shut down after the accident on the Fire Ball ride, a giant pendulum that swings riders in carts from side to side.

A spokesman for the Columbus, Ohio fire department told reporters an 18-year-old male was thrown 15m and killed on impact.

Three other people were reported in critical condition and four more were in stable condition.

Ms Rhonda Burgess, who was at the fair with her three children, told CNN the accident involved carts carrying riders that were attached to the end of the pendulum.

A piece on one cart "snapped off and the riders came out of the cart", she said.

"At least two (people) flew through the air at least 20 feet (6m) before landing on their backs on the concrete," Ms Burgess said.

Mr David Evans, director of the Ohio State University Wexner Medical Center where some of the injured were taken, likened the accident to a high-speed car crash in which the occupants are ejected from the vehicle.

"This was a great force and a great mechanism," he said.

The accident occurred on the opening day of the Ohio State Fair in Columbus.

The Columbus Dispatch said the ride, built by KMG, was billed as an "aggressive thrill".