Residents refusing to evacuate their properties in the face of a fierce bushfire south of Perth are being warned fire crews will not risk their lives for those who refuse to leave.

The fire has been raging in Northcliffe, 350 kilometres south of Perth, for six days.

Authorities said a south-westerly wind change had blown out the northern flank of the fire, which was directly lined up to hit the Northcliffe town centre.

Prime Minister Tony Abbott has offered federal assistance in fighting the blaze, which has doubled in size and burnt through 58,000 hectares with the town now considered indefensible.

There were unconfirmed reports that two houses and a number of sheds had been destroyed.

Residents were warned at a community meeting that the massive fire was a grave and imminent threat to the town.

Many evacuated to nearby Pemberton but some refused to leave.

Minister Joe Francis said they needed to understand the risk they were taking.

"They need to be ready to protect themselves because we are not going to risk the lives of firefighters for those that choose to stay behind," he said.

"They need to make sure they are fit, able to defend their properties and they have all the resources.

"That is their call."

Incident controller Greg Maires told residents at the meeting that firefighters could not keep pace with the blaze as conditions were rapidly changing.

"I must be quite frank - there is a grave and imminent threat to the Northcliffe community," he said.

Fire crews said the option of Commonwealth assistance was available in such a severe fire situation, meaning the Army could be deployed to assist with operations, such as providing tent accommodation.

Manjimup Shire president Wade de Campo said he was not sure if they would need to request further federal assistance at this stage.

"Tony Abbott gave me a call offering any federal assistance we wanted to fight the fire with," he said.

"I joked with him that he'd been under fire himself in the last few days and we had a laugh."

Mr de Campo said there had been arrangements for a military camp, dubbed "tent city", to be brought in for firefighters from other areas.

Accommodation in the area is at full capacity after the influx of personnel.

He said at least two military camps would be brought in soon which would sleep up to 300 people, with potential for more to come to accommodate up to 600 people.

'Living in a nightmare'

Authorities said there was no end in sight to the Northcliffe fire, and were preparing to fight under an emergency warning for days to come.

An emergency situation was declared for the Northcliffe blaze, providing authorities with additional powers in an attempt to minimise the severity of the fire, which had a 170 kilometres-long perimeter.

About 200 firefighters were at the scene, along with 60 support staff.

Mr Maires said several firefighters had received minor injuries.

Northcliffe resident Kathy Jones, who spent two nights at an evacuation centre in Pemberton, said she was worried about her firefighter husband.

"I feel like I'm living in a nightmare," she said.

"I'm worried about my husband, who's a volunteer firefighter who's out there. I don't think he's had any proper sleep for four, five days.

"Obviously I'm worried about my house but it's really not important, as long as he's okay."

Those who left Northcliffe faced the prospect of returning to nothing.

Cathy Rabbitt and her family fled four days ago and neighbours who stayed told her the house was still standing but everything else was destroyed.

"It's bittersweet because you have got your home, but I'm also thinking well I've just got a house sitting in a black paddock now," she said.

"We've got our own power supply, which is gone, all our water is gone, all those treasures you keep in the shed and our tractors are just not there."

Residents sent to beach at Windy Harbour

The blaze was threatening the seaside settlement of Windy Harbour. ( ABC News: Mark Bennett )

There were grave concerns for the nearby town of Windy Harbour earlier on Wednesday, where an emergency warning remains in place.

The settlement is 15km south of Northcliffe.

Steve Hughes, from Augusta, used his boat to get to Windy Harbour in case anyone needed a lift out.

"There was a lot of fire there," he said.

He said several people were on the beach.

"There were about six to eight people, mainly elderly, and a couple of kids swimming in the water," Mr Hughes said.

"They choppered the people out that needed to leave."

But he said he did not need to take out anybody on his boat.

"They were very appreciative of the beer and the steaks I brought in for them though," he said.

The fire is currently 27 kilometres from Pemberton, and if it were to follow a direct line, it would be a matter of a day before that town is directly threatened.

Out-of-control blaze in Lower Hotham

A second fire in Lower Hotham in the Shire of Boddington, about 120 kilometres south of Perth, was also out of control.

The map shows the activity of the Northcliffe fire in recent days. ( GeoScience Australia )

An emergency warning was in place for the southern part of Lower Hotham in the Shire of Boddington for a fire that authorities said was expected to triple in size over the next 24 hours.

The department said the alert level had been upgraded due to the intensity of the fire, which was still unpredictable and burning out of control.

Residents who did not plan to actively defend their home were advised to evacuate.

DFES incident controller Ross Delaney told a community meeting in Boddington that residents who had been evacuated may not be able to return for several days.

One house has been badly damaged and a shed destroyed by the fire that has been burning since the weekend in the area, around 120 kilometres south of Perth, DFES said.

The owner of the property escaped unharmed.

Residents were set to spend another night away from home.

Jenni A'Court said she left her property last night, with her husband and daughter.

"We did go back this morning but we had to leave again very much, very quickly," she said.

"Apparently they're putting fire retardant on our house now, which will do what it can do. We've already got friends that's lost a house."

The fire, which was started by lightning on Saturday, has so far burnt 12,500 hectares and the fire front was one kilometre long.

Superintendent Delaney said it could take weeks to extinguish the blaze, which was burning mostly in bushland.

He said firefighters were trying to protect mining infrastructure in the area including a conveyor belt owned by BHP Billiton and Alcoa.

About 90 firefighters were at the scene and parts of Boddington were without power.

A relocation centre was set up at the Boddington Pavilion, Club Road, Boddington.