Australian militants are now fighting with jihadists in Iraq, with one convicted terrorist believed to be among them.

Attorney-General George Brandis said on Wednesday the government had long been concerned that Australian extremists were fighting in Syria and believe some may now have crossed the border and are fighting in Iraq.

News Corp reports convicted terrorist Khaled Sharrouf is thought to be among the fighters associated with the Islamic State of Iraq and the Levant (ISIL), also known as ISIS.

Senator Brandis was unwilling to discuss details, other than to state it was believed Sharrouf had travelled to Syria.

However, Sharrouf’s social media profile showed him in military fatigues waving the ISIL flag, while counter-terrorism sources had confirmed the picture was of him and that he was believed to be in Iraq, the report said.

Fairfax media reports Australians who left to fight against the Syrian regime of Bashar al-Assad have now joined forces with ISIL and have crossed the border into neighbouring Iraq.

The report said at least several Australians had entered Iraq and had seen fighting in the north of the country.