An Australian soldier turned Al Qaeda member who dropped off the map years ago may have dramatically resurfaced as a senior combat commander fighting against Western forces in Syria.

Mathew Stewart, now aged in his late thirties, fled Australia in 2001 for war-torn Afghanistan, where he joined Al Qaeda in the months before the September 11 attacks.

Little has been heard of him since.

That changed on Sunday night, when Al Qaeda published its latest online magazine about Syria, Al Risalah.

The magazine included an interview with an Al Qaeda member known as Usama Hamza Australi.

He describes working as a military trainer with Al Qaeda's proxy in Syria, Jabhat Al Nusrah.

In the interview Hamza discusses his background, saying he is originally from Queensland, joined Al Qaeda 15 years ago, and previously served in the Australian military.

That description matches Mathew Stewart exactly.

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The Australian Federal Police declined to comment on the magazine interview.

A law enforcement official, speaking on condition of anonymity, told 7.30 authorities were aware of the interview and were working to see if they could definitively establish if Hamza is Stewart.

'I truly believe that Al Qaeda's methodology is the right way'

The news of the interview was broken today by US website The Long War Journal, though they were unaware of the link between Usama Hamza Australi and Mathew Stewart.

Stewart's new role, if proven, makes him one of the most highly-ranked Australians fighting in Syria.

Another Australian citizen, Moustafa Mahamad — also known as Abu Sulayman al Muhajir — is also a senior member of Jabhat Al Nusrah, though he plays a mainly theological and motivational role.

In the Risalah interview, Hamza discusses the difference between Jabhat Al Nusrah and Islamic State.

Since late 2013 Nusrah and Islamic State have been feuding over whose interpretation of Islam is more correct, and who is the legitimate leader of the many militant Islamist groups in Syria waging an insurgency against Syrian dictator, Bashar al-Assad.

Al Qaeda is concerned it is being replaced by Islamic State as the vanguard of the global militant Islamist struggle against the West, and is seeking to cast itself as the more moderate force and properly Islamic of the two groups.

"I truly believe that Al Qaeda's methodology is the right way, the way of mercy, the way of forgiveness ... the way of strength, and strength is not just in killing," Hamza says in the interview.

He also describes his role as a military trainer.

"Training tactically, working in small ... I hate to use the word 'commandos' ... high standard infantry tactics, long-range patrols, reconnaissance patrols, ambushing, raids, sabotage, harassment behind enemy lines, reaction to combat, how to fight with the enemy in a guerrilla warfare scenario, targeting convoys, targeting installations behind enemy lines with no support, and so on.

"These were some of the things I trained in for a number of years with the Australian military, and then experienced [in the battlefield] for almost 15 years in Afghanistan [and here in Syria]."

'Any chance I get to fight I'm there'

He also reveals his role in Al Qaeda's military operations in Syria.

"I'm a trainer who still lives to fight," he said.

"Any chance I get to fight I'm certainly there, and any input, then I am certainly there."

Stewart served with the Australian army as an infantryman and deployed to East Timor in 1999.

He served there for six months and media reports at the time suggested he was then diagnosed with post-traumatic stress disorder.

He left the Army in July 2001 and less than a month later flew out of Australia, bound for Afghanistan.

In 2005 an Al Qaeda video featuring a man wearing a balaclava and speaking in an Australian accent was released.

The speaker criticised Western values and called on the US and UK to withdraw from Afghanistan and Iraq.

Stewart's family said the speaker was not Stewart, but the Federal Government had its doubts.

Years later it was rumoured that he was killed in a US air strike somewhere near the Afghanistan-Pakistan border, but that was never proven.