HELENSBURGH police are on the lookout for a dog owner whose pet allegedly attacked a female runner.

A 39-year-old woman was said to have been out running on the trails behind the Hill House on Sunday evening, May 10 when a brown and white collie dog bit her on the leg.

Police say the bite fortunately did not break the skin, though it did leave bruising.

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The male owner of the animal is described as in his twenties, 5ft 10in tall and of slim build. It's understood that he caught up with the dog before taking it under control.

The man was said to have been accompanied by another woman who also had a dog – a grey coloured whippet – with her, and the pair reportedly walked away from the victim without providing their details.

Anyone who may have any information regarding the identity of the man is asked to contact PC Haining at Helensburgh police office.

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