A woman on a mobility scooter has been hit and run over by a truck on State Highway 2.

The woman is understood to have suffered serious head injuries in the crash, which happened in the centre of Katikati at 12.45pm outside Subway.

Members of Tauranga's Serious Crash Unit are at the scene and the woman has is being treated by firefighters and ambulance staff.

A reporter at the scene said traffic was being diverted at each end of the town centre, with no traffic travelling through.

Shaken witnesses were being spoken to by police.

The woman had been travelling on a mobility scooter on the main road, near a pull over bay when she was struck and went under, the reporter said.