Read more: Is Banksy really in Tauranga?
A Tauranga City Council spokeswoman Viktoria Ermes said it had no idea who had done the street art.
''We know nothing about it. It's nothing initiated by us.''
Ms Ermes said the mysterious piece was great because it sparked conversation and intrigue, ''which is what street art is meant to do''.
The council, in partnership with Oi You! and Tauranga Art Gallery, is bringing the 2017: Paradox: Tauranga Street Art Festival, which will run from March until the end of June.
Festival director George Shaw said he also knew nothing about the art work and did not know who was responsible for it.
''What's interesting is this piece appears to have had more time and care put into it than the others.''
Last week, two Banksy-styled artworks also appeared in central Tauranga - with no apparent owner.
''If you look at the detail in it, it has been a very well delivered stencil,'' Mr Shaw said.
Darryl Milne, who worked a few stores down from the mural, said he had not seen it before.
He said the thought of Banksy being in town was "really cool".
A woman walking to work this morning told the Bay of Plenty Times she had not seen it there yesterday.
The arrival of the mural comes on the heels of Mr Key's shock resignation yesterday afternoon.
Mr Key will formally step down as Prime Minister and leader of the National Party on Monday.
