Terror accused was lonely: Father

The father of a Sydney man charged with planning a terrorist attack says his son was lonely in Australia.

Omar al-Kutobi, 24, was working as a removalist and studying nursing after he failed to find a job in IT, his father Ahmed told Fairfax Media from Germany.

"He told (me) many times to come to him because he is alone," he said.

Omar al-Kutobi and his friend Mohammad Kiad, 25, were arrested at their western Sydney granny flat on Tuesday afternoon.

But Al-Kutobi's father said he suspected nothing untoward when he spoke to his son by phone on Tuesday.

"He told me (he) was working as a truck driver and asked me about his mother," he said.

"That is all. Everything was okay."

He said he had paid thousands of dollars to send his son to Australia in 2009, away from the violence of his homeland of Iraq.

He said his son loved Australia and became a citizen in 2013.

Neighbours described al-Kutobi and Kiad as private and quiet.

The two men are due to appear in a Sydney court on Thursday.