Nearly a dozen homes and two sheds have been razed as strengthening winds pose fresh concerns for firefighters tackling the massive Port Hills wildfire now burning fiercely on three fronts.

Hundreds of Christchurch residents have been evacuated and police warn many may still have to go at a moment's notice if the firestorm suddenly changes direction.

Civil Defence revised the number of properties destroyed in the fire saying 11 houses and two sheds had been lost in the ferocious fire. Four homes were in Worsleys Rd, four were in Hoon Hay Valley Rd, one house and one shed on Burkes Bush Rd, and two houses and one shed on Early Valley Rd.

Authorities are now concerned about today's weather forecast, fearing a strong northeast wind will further fan the fire and drive the fronts into residential areas.

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The MetService is forecasting strong winds of up to 45km/h will blow across the city this afternoon.

Fire crews plan their next move tackling the massive wildfire burning on Christchurch's Port Hills. Photo / Christchurch City Council
Fire crews plan their next move tackling the massive wildfire burning on Christchurch's Port Hills. Photo / Christchurch City Council

Emergency services have been out since first light focusing on the super fire's three fronts at Worsleys Rd, Early Valley Rd and Governors Bay.

The deadly blaze, which started in Marleys Hill on Monday night, now spans 1800ha.

At this stage firefighters are preparing to continue operations over the weekend.

The immediate emphasis was on directing the huge fire away from people and property.

The Fire Service said today's effort involves 15 helicopters and planes — the maximum number that can safely be in the air at any one time — ground firefighting crews from the New Zealand Fire Service, Department of Conservation, territorial authorities, and volunteers.

Helicopters have been brought in from throughout the South Island as well as more firefighters from Nelson and Timaru.

More than three dozen fire trucks were stationed at the fire fronts.

To date 400 homes had been evacuated by police and defence personnel and hundreds of residents have chosen to leave as a precaution.

No evacuations are under way at this time but police warned the situation was extremely volatile and should the fire change direction people may have to leave at short notice.

Christchurch police superintendent John Price said patrols were also working around the clock in evacuated areas and those at risk of fire.

"We are providing reassurance to residents about evacuation, but also to others that we are keeping a watchful eye on their property," he said.

Welfare and health agencies were on standby, ready to step in at a moment's notice.

St John had dealt with a number of minor issues.

About 11 evacuees were at the Te Hapua Halswell Centre.

Catering was being provided with donations from the local supermarket.

A welfare centre also remained open at Nga Hau e Wha National Marae on Pages Rd.