What happens to Australia if North Korea launches an ICBM in our direction?

As tensions rise between the US and North Korea with the rogue state claiming its ballistic missiles are capable of hitting "anywhere in the world," concerns have been raised over just how tangible the threat is for Australia.

After Kim Jong-un threatened the small US Pacific island territory of Guam, former prime ministers Tony Abbott and Kevin Rudd are pushing for urgent upgrades to Australia's missile defences, especially in the country's north.

On Tuesday, state media from the Democratic People’s Republic of Korea (DPRK) released images of Kim Jong-un reportedly viewing maps and attack plans for Guam, an island in the Pacific home to a US military base.

Guam falls less than 3500km from North Korea, but it has been suggested the intercontinental ballistic missiles (ICBM) being developed by the rogue nation could have a range of up to 8000 kilometres.

That would put some Australian cities and regional centres within range of the DPRK’s weaponry.

Speaking with Fairfax Media on Thursday, Mr Abbott said: "Of course we should be able to defend ourselves if they have missiles that can reach Australia”.

Director of the Lowy Institute's International Security Program, Euan Graham, said if the missiles were capable of travelling thousands of kilometres, it was not only northern Australia under threat, but much of the mainland.

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Both Mr Abbott and Mr Rudd have called for a missile defence shield, similar to America's THAAD system, which has been deployed in Guam, Alaska, Hawaii and South Korea in recent months.

But Defence Industry Minister Christopher Pyne dismissed the missile shield idea as "patently absurd".

He said it would cost tens of billions of dollars, take years to build and would be useless against the intercontinental, long-range missiles.

Defence experts have also pointed out it would be "Costly and unreliable" as Australia was too vast to be covered by an adequate missile defence shield.

Australia is one of the only US allies to not have a missile defence system and experts have said aiming one toward North Korea could be seen as a "tactical opportunity".

"If we're looking at US allies that don't have missile defence capability, Australia is the standout," Mr Graham said.

Last week, Prime Minister Malcolm Turnbull confirmed the nation would come to the aid of the US if it were attacked, insisting the two nations were “joined at the hip” on defence.

"If there's an attack on the US, the ANZUS Treaty would be invoked and Australia would come to the aid of the United States, as America would come to our aid if we were attacked," he said.

But Mr Rudd accused the prime minister of acting irresponsibly and giving our larger ally a “blank cheque”, saying there was no need to lock in specifics.

"You never as an Australian prime minister, as an ally of the United States, give the Americans, before the event, a blank cheque," he said.

Writing in the Financial Review, Professor of History at Sydney University James Curran suggested Australia offers the US “unflagging support at every turn” in the hope our “great ally will return the favour come what may”.

Historically however, that has not always been the case, as Curran points out the ANZUS treaty only offers a guarantee for the parties to consult and “act to meet the common danger in accordance with its constitutional processes”.

When North Korean dictator Kim Jong-un threatened to launch missiles toward the small US territory of Guam, President Donald Trump retorted he would meet ongoing threats from Pyongyang with "fire and fury".

On Tuesday, Kim backtracked on the threats, but warned he could "change his mind".

Satellite images revealed the same day also captured North Korea moving missiles into position.

Other photos, of North Korea's military bases appear to show submarine activity at a test site.

The pictures reportedly show tarps and netting installed above the SINPO-class submarine to "obscure any activity taking place beneath them".