Australian Formula One racer Mark Webber has been seriously injured after being hit by a car while competing in his multisport challenge in Tasmania.

Webber, who drives for F1's Red Bull team, was cycling along Fortesque Bay Road, near Port Arthur on the Tasman peninsula, when he and a Nissan X-Trail vehicle collided, Tasmania Police Sergeant Jon Ford told AAP.

Sgt Ford said Webber was competing in his own charity event, the Mark Webber Pure Tasmania Challenge, a 250km challenge using mountain bikes, kayaks and trekking, when the accident happened, around 12.40pm (AEDT) on Saturday.

"As a result of the collision, the rider, Mark Webber, suffered serious but non-life threatening injuries," Sgt Ford said.

"He was attended at the scene by paramedics attached to the event before being airlifted to the Royal Hobart Hospital."

Sgt Ford said the event was being raced on open public roads and it was not known whether the stage along Fortesque Bay Road was cordoned off specifically for the racers.

The male driver of the Nissan X-trail escaped injury but no further details were known about the motorist, he added.

Webber was competing on the penultimate day of the five-day challenge, which also includes abseiling and whitewater rafting.