A man brandishing a metal hammer attacked a woman inside her car after she stopped on the side of the road to adjust her radio, police say.
Hamilton Police have launched a manhunt for the offender, described as being Maori and in his early 20s.
The attack happened at about 12.30pm yesterday on Tramway Road in Enderley, police said.
The 27-year-old woman had been driving along the road before pulling over to adjust her stereo.
She was approached by an unknown man brandishing a large metal hammer, police said.