A contingent of Kiwi firefighters are joining their counterparts across the Tasman to combat wildfires blazing in Victoria.

The 23-strong team leaves from Auckland, Wellington and Christchurch for Melbourne this afternoon, to join efforts centred around the coastal town of Lorne, where fires have already destroyed about 120 homes.

More homes and infrastructure remain under threat as drought conditions and moderate winds fuel fires around the area and further along the Great Ocean Road, south of Melbourne.

"Our firefighters will be containing fires around some of the townships and working to protect homes and other buildings in these towns," national rural fire officer Kevin O'Connor said.

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The fires were sparked last month by lightning strikes, and are still burning in dense forest, having already destroyed 2500 hectares of vegetation along a 40-kilometre front.

They were threatening Great Otway National Park, the Mount Cowley tower and some water supply catchments, including those for Barwon and Lorne.

Mr O'Connor said a second contingent of 22 firefighters would leave on January 11 to bolster New Zealand's contribution.

Both deployments were expected to last three weeks, with a possible extension depending on conditions, which were extreme in Victoria's southern coastal areas.

The firefighters were drawn from rural fire authorities around the country, including staff from Department of Conservation and forestry companies.

"Working conditions will be arduous, with steep and inaccessible terrain, plus high temperatures. Numerous aircraft are currently working on the fires."

Today's deployment would be the 17th overseas by rural firefighters since 2001 -- the ninth to Australia and the sixth to Victoria.