SYDNEY (AFP) - An 18-year-old Australian man was behind a deadly suicide bomb attack in Iraq last week, authorities said Monday, with Attorney-General George Brandis calling it a "disturbing development".

The blast last Thursday near a mosque in Baghdad left several dead, including the teenager, who left Melbourne for the region last year.

Reports said the Islamic State militant group named him as Abu Bakr al-Australi on an affiliated Twitter feed, with Brandis' office confirming he was Australian.

"This is a disturbing development and is a further example of the dangerous and volatile situation in Iraq at present," Brandis said in a statement.

"The government deplores the violent actions being undertaken by ISIL and other extremist groups in Iraq and Syria, and is deeply concerned about the involvement of Australians in these activities.

"As I have said many times, it is illegal for Australians to engage in the conflicts in Iraq and Syria and the government urges Australians not to travel to the region."

The statement said he was the second Australian suicide bomber in the Iraq and Syria conflicts, without providing further details.

Last month Foreign Minister Julie Bishop said she was deeply concerned that about 150 Australians, some dual citizens, were learning the "terrorist trade" fighting alongside Sunni militants in Iraq and Syria.

"The participation by Australians in the conflict in Iraq and Syria poses a significant domestic security threat to Australia when those involved return home and seek to pursue violence here," said Brandis.

"The government will continue to take all necessary measures to keep Australia and Australian interests safe."