An alleged sexual assault on a female runner near the Ross Creek reservoir in Dunedin was most likely a "random'' attack, police said today.
The 23-year-old was knocked to the ground, tied up and assaulted about 9.15pm yesterday, police said.
Detective Senior Sergeant Kallum Croudis told media late this afternoon the incident took place just off a main track in Ross Creek and was most likely a "random" attack.
Police are concerned, as such crimes were "very rare'' in Dunedin, he said.
The man fled after a dog, possibly a Labrador, ran up to them, surprising both.
After the man left the area, the woman managed to free herself, but was initially too scared to leave the scene in case he was still there.
Mr Croudis said the public should be vigilant and report any suspicious activity.
Scientists from ESR had been called to help examine the scene this afternoon.
Police earlier today released a description of the man sought.
He was European, tall, of skinny build and of an undetermined age. He was believed to have been wearing black shoes, a black T-shirt, and a pair of black `Skins' with white writing.
Police said they have spoken to the owner of a light-coloured dog, but want talk with anyone else who was walking a similar-coloured dog in the area about 9pm.
They urged anyone who was near Ross Creek at the time, or who saw a man matching the description of the alleged attacker, to come forward.
A team of more than 20 detectives and uniformed staff was involved in the operation.
The area would remain cordoned off today to allow a scene examination to take place.
Anyone with information could call the Dunedin Central Police Station on (03) 471 4800. Alternatively, information could also be passed on anonymously via the organisation Crimestoppers on0800 555 111.