An Auckland man has been left bloodied and suffering minor injuries after a shark bit his arm at Papamoa Beach in the Bay of Plenty.

The attack - by what the man described as a baby shark - comes as the Department of Conservation (DOC) is calling for caution at nearby Tauranga Harbour this long weekend after several possible great white shark sightings.

"It gave me a fright, thankfully it didn't latch on, and by the time I came to the surface it was gone," the man told Stuff following the incident on Wednesday evening. "I rubbed the water out of my eyes once I breached the surface and as I did I felt like a big rush of water, I assume from its tail, whip past me."

"I got to shore and saw a guy about to head into the water. I stopped him and explained what had happened. We both then ushered the other nine or so people out of the water – a couple of kids too."

He did not require hospital treatment, but the close encounter with the shark - species unknown - comes as the Department of Conservation warns about great whites in nearby Tauranga Harbour.

People should be aware and avoid swimming in the main channels of the harbour or fishing from kayaks and jet skis, the organisation advised.

DOC marine technical advisor Clinton Duffy said the public needed to remember they were sharing the coastal waters with a number of different shark species.

"There are always sharks around our coastline and at times they may come close to the shore."

He said there had been several confirmed and unconfirmed sightings of great white sharks in Tauranga Harbour recently.

"It is not unusual for them to be there, however when we're visiting the ocean, we need to be a little bit vigilant and aware of what's happening around us. Swim where there are surf lifesaving patrols, and don't swim or dive alone."

Great white sharks are protected under the Wildlife Act 1953 and is illegal to hunt, kill or otherwise harm them.

Other species of shark protected in New Zealand include the basking shark, the oceanic whitetip, the small tooth sandtiger (deepwater nurse shark) and the whale shark.