MORE than 3000 litres of diesel have leaked into a New Zealand harbour from a ship and more is continuing to spill as a cleanup team assesses options.

Authorities were notified about 5.45pm on Friday by which time about 3000 litres of diesel had already spilled from the ship into Napier Harbour.

A Hawke's Bay Regional Council spokesman told AAP a cleanup team was at the scene assessing the situation so they could work out how to stop the leak and mop up the mess.

He could not say how the leak started or exactly where the ship was in the harbour.

The harbour, where a number of recreational boats are moored, may be closed overnight.

Both fire and police staff have attended but have handed control of the cleanup over to council staff.

Fairfax are reporting that the spill is about 300m wide and is situated near the Napier Sailing Club near Pandora Road.

Originally published as Large diesel spill in NZ harbour