Extra fire crews are being brought in today to try and contain a large blaze on conservation wetlands at Awarua, south of Invercargill.

Awarua-Waituna, one of New Zealand's largest remaining coastal wetland systems, is threatened by the fire south of Invercargill. 

The fire which started on Saturday and extends from the head of Awarua Bay to the Waituna Wetlands has burnt through about 1000 hectares containing peat.

Fire and Emergency said it is almost guaranteed to get bigger today, with a change in wind direction forecast for this afternoon.

This will bring easterly gusts up to 45 knots, blowing the fire toward unburnt land rather than away from it.

Awarua Bay Road has been closed to the public and people are asked to stay away from the area.

Nine Helicopters and eight ground crews will resume fighting the fire at 8am today this morning, with heavy machinery used to create fire breaks.