A man was attacked by a dog after an altercation with another man on Albert Road, Southsea.
It is believed that following the altercation, a man set his dog on another man.
The victim had puncture wounds to his arm as a result of the incident.
PC David Freeman said: "This is an apparent directed attack by a bull terrier type dog. I want to deal with the suspect and the dog responsible for this incident as soon as possible in order to prevent it happening to anyone else.”