![Execution of search warrants across Sydney's north-west suburbs Execution of search warrants across Sydney's north-west suburbs](/images/transform/v1/crop/frm/silverstone-feed-data/3773b02d-9060-4844-a3f5-788fd1b887a7.jpg/r0_0_620_413_w1200_h678_fmax.jpg)
Counter-terrorism authorities have used for the first time extraordinary, Howard-era powers to hold in secret and without charge three suspects arrested in Thursday's terror raids.
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In a statement late on Friday, Australian Federal Police revealed they had used preventative detention orders to hold the three men without charge for about 36 hours before releasing them on Friday afternoon.
Preventative detention orders can be used only ''where there is a threat of an imminent terrorist attack'', suggesting authorities were concerned the men would go ahead with an attack if they were released earlier.
The prevention orders were granted by the Supreme Court of NSW on Wednesday before the raids.
As the nation continued to come to grips with allegations of an Islamic State plot to murder Australians on camera, Prime Minister Tony Abbott confirmed that an attack was expected ''within days'' had authorities not moved when they did.
The Prime Minister said police ''expect further charges to be laid against other individuals'' from among the 15 people arrested in the dawn raids.
Of those, an unknown number, believed to be between two and four, were still being held on Friday - suggesting police are using special terrorism powers passed after the 2005 London bombings.
''It is a serious situation when all you need to do to carry out a terrorist attack is to have a knife, an iPhone and a victim,'' Mr Abbott said.
AFP acting Commissioner Andrew Colvin told a Friday media conference that ''a number of people are still being detained'' but refused to say how many.
Under laws introduced by the Howard government after the 2005 London bombings, a person can be held for up to 14 days under a ''preventative detention order'' if authorities believe ''there is a threat of an imminent terrorist attack''. This power has never before been used.
The powers are due to expire next year because of a ''sunset clause'' written into the legislation. But under a raft of counter-terrorism laws the Abbott government plans to introduce to Federal Parliament next week, the powers would be kept going for another 10 years.
The alternative reason that the remaining suspects might still be held without charge is if police need to gather more evidence, in which case they can repeatedly get 24-hour extensions with an order from a magistrate.
Thursday's raids were launched after police intercepted a phone call between Mohammad Ali Baryalei - a top Australian terrorism recruiter believed to be in Syria - and Sydney man Omarjan Azari in which they allegedly discussed plans to snatch a member of the public off a Sydney street and kill them in front of a camera. The video would then be sent to the Islamic State's propaganda wing to post online.
Mr Azari, 22, has been charged with conspiring to plan or prepare a terrorist act, which police allege was intended to ''shock, horrify and terrify the community''. One other man has been charged with firearms offences and released on bail.
Mr Colvin stressed that Thursday had been ''very much a disruption exercise''. ''We should not for one minute think that this investigation has now reached its conclusion,'' he said.
Fairfax Media understands the bulk of the property police seized during Thursday's raids was communications equipment.