Two helicopters and up to 40 firefighters are battling a bush fire threatening three or four homes on Auckland's North Shore

Fire and Emergency say they were alerted to a fire in trees and thick bush near Okura River Road about 2.20 this afternoon.

Shift manager Colin Underdown says the fire's being fuelled by an easterly wind and covers about five hectares.

He says four water tankers and six fire engines have also been at the scene.