Sydney terror suspects may have arrived in Australia with false documents: Dutton

Immigration Minister Peter Dutton has asked for an urgent review following suggestions one of two Sydney terror suspects may have entered Australia with false documentation.

Police will allege that Omar Al-Kutobi, 24, and Mohammad Kiad, 25, were about to kill or harm a member of the public with a knife as part of a terrorist attack.

They were arrested on Tuesday afternoon at a property in Sydney's west.

Mr Dutton says he's been advised one of the suspects might have flown to Australia with false documentation in 2009.

He said there were about 50,000 people who also arrived on boats around that time, hampering intelligence agencies' ability to check every person thoroughly.

"It is a difficult situation, particularly that period of time, for the intelligence agencies," he told Nine Network on Thursday.

"I've asked for an urgent review, in relation to all the facts in relation to this case, so that we can learn lessons."

"Borders, at that stage, were fairly porous in Australia, with boats just coming every day.

"If the system is being overwhelmed by tens of thousands of people coming by boat, it doesn't matter if they come by boat or plane, it's pretty hard for the security agencies to conduct the thorough searches they need to conduct."

The men appeared before Fairfield Local Court on Wednesday and didn't apply for bail, which was formally refused.

They are due to appear at Central Local Court on Thursday via audio visual link.