A Greytown man who opened his window in the early hours to see several buildings on his street ablaze said the scene was like "Armaggedon".

Firefighters have been battling the fires since about 4am, and are treating them as suspicious.

A local man on Wards Line said he woke in the early hours to the sound of banging, and thought someone was out shooting.

"But it got louder and I thought 'no, that's not shooting,'" he told NZME.

He opened his window to see the house north of his was on fire. He then opened the curtains and realised two homes, a barn and several outbuildings were also on fire.

"I thought 'it's Armaggedon' . . . it was terrifying."

The scene at Wards Line. Photo / Mark Mitchell

The resident got dressed and went outside to find one of the neighbours whose home it was running down the street.

He took her in and gave her a hot drink, and her husband too when he arrived.

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He said their smoke alarms woke them and they fled their house with just the clothes on their backs.

The couple had an idea of how the fires started, but the man was "not at liberty to say".

"I guess it will all come out in the wash."

He said the couple were "doing fine".

"They're alright, they've got good neighbours. Good neighbours look after each other."

The man's wife said the incident was "horrendous".

Carterton Mayor Ron Mark had spoken to firefighters at the scene and said, while the cause was still to be confirmed by police and fire investigators, it appeared the fires were started on the outside of buildings, with multiple structures catching fire.

"You know, one after the other indicates highly an arson attack to them."

Mark has told Stuff that one of the buildings was set on fire while firefighters were trying to put out a separate blaze.

Police are assisting Fire and Emergency NZ at the scene. Photo / Mark Mitchell

Authorities are investigating the circumstances behind the suspicious fire in several homes and buildings on Wards Line.

A neighbour across the street from the blazes said they knew all the people affected and it was "pretty devastating for everyone".

The homes and at least one barn are affected at two locations on the same road.

When fire crews arrived, they realised other homes were on fire on the same street - and raised the situation to a fourth alarm.

Up to eight fire engines and three tankers were at the scene as well as other support vehicles, but the fires have now been put out.

There are no reported injuries at this stage. However, authorities confirmed the fire is being treated as suspicious and up to five specialist investigators are at the scene.

'Smoke and flashing lights everywhere'

A resident on Wards Line said fire crews remain at the scene, as of 7am.

"It's pretty bad. It's two houses and some farmhouses."

Asked if she had heard any explosions or anything else that may have alerted them to a fire early this morning, she said they had not heard anything.

Another resident, Brian Tucker, said police and firefighters had swarmed the area.

"There's a lot of responders here - police and fire people. Not sure what's caused it. It sounds suspicious, but nobody's hurt.

At least two homes, a barn and some outbuildings were alight. Photo / Mark Mitchell

"There's a lot of smoke and flashing lights."

Police also confirmed they are assisting Fire and Emergency NZ at the scene.

Police were told of "multiple houses" on fire just before 4am.

TVNZ's Breakfast said they understood up to five properties are affected - at least two homes and barns.

A reporter at the scene said residents at the first house that alerted fire crews were seen wearing blankets and speaking to authorities outside.

They had been allowed back into their home for a short time to gather a few items, Breakfast reported.

Large plumes of white smoke could be seen billowing from one of the properties in the background.

Police confirmed they were assisting FENZ following reports of multiple fires on a rural property in the South Wairarapa.

Police were notified at around 3.55am and arrived to find multiple structures involved on Wards Line in Morison Bush.

Police and FENZ will be doing scene examinations as part of identifying the circumstances surrounding the fires.

Police will be deployed in the area today engaging with the community as part of the investigation.

Police would like to speak with anyone who was in the area of Wards Line between 2am and 4am today.

Contact can be made through the Police 105 line, referencing P052198593.

Information can also be provided to Masterton Police Station on (06) 370 0300.