The passport of a Melbourne schoolboy apparently killed carrying out a suicide bombing in Iraq overnight was cancelled in October last year, just months after the teenager left Australia to fight with Islamic State.

Islamic State claims the schoolboy, who converted to Islam aged 16 after self-radicalising on the internet, died in a series of co-ordinated car bombs across the city of Ramadi.

Foreign Minister Julie Bishop says the government is trying to independently verify Mr Bilardi's death and has been aware of his presence in Iraq and Syria "for a number of months".