At just 19 years old, Bankstown labourer Abu Bakr is the face of jihadism in Australia, ASIO says.

The outspoken teenager ''holds an extreme ideology and is planning to travel in order to engage in militant extremism'', the national spy agency has concluded.

On Sunday, Fairfax Media revealed Abu Bakr was one of at least 20 men whose passports have been cancelled by ASIO on the grounds they were prepared to engage in politically motivated violence or had a ''jihadist mentality''.

But Abu Bakr said it was unjust and racist labelling amid a crackdown on Australians taking part in the Syrian civil war.

Last week, two men were charged under foreign incursion laws, including Sydney pensioner Hamdi Alqudsi, 39, who allegedly organised and paid for six men to travel to Syria this year to fight with terrorist organisations.

Lawyer Zali Burrows, representing the 20 Australian Muslims, said she would launch a class action against the government and expected more to join it.

Abu Bakr, who was born in Australia of Iraqi and Italian heritage, went to Auburn West Public School and Birrong Boys High School. He said his ''brothers'' had been randomly targeted by intelligence authorities since the conflict in Syria began.

He believes he drew the gaze of ASIO because he recorded himself delivering a series of lectures on Syria and posted them online. ASIO said it would not comment on specific cases.

Its investigation concluded he planned to travel abroad to engage in violence, so his passport was cancelled. He will be refused a new one should he apply.

''If you refuse to be silent on something, on the injustice, on the evil, on the raping and killing and bombing in Syria, then they label you a jihadist or a fanatic or an extremist,'' Abu Bakr said.

The Syrian war led to more passports being cancelled by ASIO in the past financial year than before, the agency's annual report says.

The definition of ''jihadist'' was problematic because it was so unclear, said University of Sydney academic Jan Ali, who is researching radicalism among young Muslims.

He said ASIO could label someone a jihadist on the basis they shared the attitude of a jihadist or made a Facebook post about jihad.

''A jihadist is generally seen as an individual who is perceived to engage in a war against the West and is prepared to cause harm,'' he said. ''It can also manifest itself in simply having that attitude. That can be just as dangerous as the action.

''The ASIO claim would be, 'Yes, we know you didn't do anything but we have got evidence or we believe that you are going to do that', and that, in itself, is enough.''

Abu Bakr said he was not planning to travel anywhere. He has refused to hand over his passport and has vowed to fight the order.

Wissam Haddad, a spokesman for the 20 men, said he knew of at least 45 Sydney Muslims who have had their passports cancelled or bank accounts frozen, often without warning or the ability to provide evidence in their defence.

Mr Haddad said the men were so incensed that, if they could, they would leave the country and not return.

''They want to send the message that, if their government is saying they are such a danger, why leave them here? These people are willing to hand in their citizenship and not return if they're not welcome here.''