Three thousand Australian Defence Force reservists will be deployed to help with the bushfire recovery, Prime Minister Scott Morrison has announced.

Key points: The Navy's largest amphibious ship, HMAS Adelaide, will sail from Sydney this afternoon to the south coast

The Navy's largest amphibious ship, HMAS Adelaide, will sail from Sydney this afternoon to the south coast Defence Minister Linda Reynolds said the compulsory call-out of the 3,000 defence reservists is a first in the nation's history

Defence Minister Linda Reynolds said the compulsory call-out of the 3,000 defence reservists is a first in the nation's history Mr Morrison also confirmed his scheduled visits to India and Japan later this month have been postponed

Mr Morrison said the Federal Government would also invest a further $20 million to lease four additional firefighting aircraft.

The Prime Minister also announced Chinook helicopters from Townsville and other military aircraft would assist, as well as the opening of defence force bases from Adelaide to Brisbane for emergency short-term accommodation.

The Navy's largest amphibious ship, HMAS Adelaide, will sail from Sydney this afternoon to sit off the coast should it be required to help with evacuations.

"They will sail this afternoon, they will be located offshore from the fire-affected areas from tomorrow afternoon," Mr Morrison said.

"The Adelaide is fully equipped for disaster relief and humanitarian aid, is able to operate helicopters, 400 crew including medical staff, as well as 300 tonnes [of emergency relief supplies] which have been loaded up in recent days."

Mr Morrison said the deployment in South Australia would focus on Kangaroo Island, after two people died in a bushfire there.

A convoy of trucks boarding HMAS Adelaide with stores, fuel, water and generators headed for the south coast of NSW. ( ABC News: Alison Branley )

It brings the nationwide bushfire death toll to 23 since September.

'Political advertising' released hours after announcement

Hours after the announcement, Mr Morrison's office released a social media video outlining the arrangements.

The post, released on Twitter and Facebook, is set to upbeat music overlaid with video of the disaster relief efforts.

"We're calling out up to 3,000 Defence Force Reservists to help in fire-affected areas," it reads.

"We've also deployed three Australian Navy ships...that's on top of the $26 million already committed this year."

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The video was slammed as "political advertising" on Twitter, with former ABC broadcaster Barrie Cassidy labelling it "absolutely obscene".

"They are advertising their responses to the fires - promoting themselves - at the height of the crisis," he said.

Elly Baxter commented: "Really? A party political ad about disaster relief. There is something seriously wrong with everyone involved with this."

Matt Burke said he had "never seen a politician's ad like this for natural disaster response with such an upbeat election feel".

But the video received a warmer response from some on Facebook, with commenters on Mr Morrison's Facebook page praising his leadership.

Reservist callout a 'first'

Defence Minister Linda Reynolds said the compulsory call-out of the 3,000 defence reservists was a first in the nation's history.

"The Government has not taken this decision lightly. In fact, it is the first time that reserves have been called out in this way in living memory and, in fact, I believe for the first time in our nation's history," she said.

Ms Reynolds said reservists who were already engaged in the current emergency response would be exempt from this call-out.

"That includes reservists who are already providing service in volunteer fire services, state fire and rescue [services], state and federal police, ambulance, and [those involved in the] emergency repair of power and communication," she said.

"Any reservists who find themselves, their family or property under threat from fires, of course, will also be exempt from this call-out."

Australian Army and Royal Australian Navy members prepare to board HMAS Adelaide. ( Supplied: Department of Defence )

Ms Reynolds said the reservists would have four key responsibilities:

1. Provide isolated communities with life-saving supplies for immediate relief 2. Provide evacuation assistance to vulnerable people in isolated communities 3. Assist with assessment and reopening of vital roads 4. Assist fire services with preparation of fire breaks away from the fire fronts

Labor leader Anthony Albanese welcomed the Federal Government's expanded emergency bushfire response and said he asked the Prime Minister to consider the extra measures months ago.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 53 seconds 53 s Anthony Albanese says he asked the PM to consider the extra measures months ago

"It's a good thing that that investment is now happening," he said.

"It's one of the things we put on the agenda for the November COAG meeting that we proposed in writing to the Prime Minister and it's good he's taking up Labor's suggestion that we made at that time."

Mr Morrison said two waterbomber aircraft would arrive within seven days, with the other two available within two weeks.

"What we need are waterbombers that meet the technical and specific requirements of the deployment in Australia," he said.

"It's not a matter of just trying to hustle up some planes from somewhere around the world.

"What you need is the precise asset to deal with the situation in Australia, NAFC [National Aerial Firefighting Centre] is an organisation we work through to source and locate the specific aircraft that we need and meet those payments.

"Two of those will be available within seven days and the others will be available within 14 days is my advice. We received the request at 8:00pm last night and we have actioned it today."

Mr Morrison also confirmed his scheduled visits to India and Japan later this month had been postponed.

He was due to visit India from January 13 to 16 and Japan immediately afterwards.

Mr Morrison came under fire for taking a family vacation in Hawaii as the bushfire crisis unfolded in December.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 58 seconds 58 s First of evacuees from Mallacoota bushfire arrive in Hastings.

Bushfire evacuees from the Victorian town of Mallacoota in East Gippsland, on Saturday arrived in Hastings on Navy ships.

About 4,000 people, including some 3,000 tourists, had been stranded in the town since they were forced to shelter on the foreshore as the fire approached on New Year's Eve.

On Friday, about 1,000 people were ferried to the naval vessels HMAS Choules and MV Sycamore.