A man naked from the waist down stopped to pick up two Chilean women hitchhiking on the West Coast.
The incident happened on Friday on Main South Road at Karoro near Greymouth.
When one of the women opened the front passenger door and realised the driver was not wearing pants, she quickly closed the door and told her friend not to get in. The pair continued walking along the road, but the man followed them slowly for a few minutes before driving off.
The driver has been described as aged about 70, European, balding, with a grey goatee beard, of thin build and about 1.88m tall. The vehicle he was driving was coloured grey and a cross between a jeep and a car.
Police have been unable to identify the culprit and are asking for anyone who witnessed the incident or know the man to contact them.