Usman Khawaja's Brother Caught Up In 'Notebook' Terror Probe

The brother of Australian cricket star Usman Khawaja has been drawn in to a police counter-terrorism investigation.

Ten Eyewitness News has learnt officers this week raided the Sydney home where Arsalan Khawaja lives with his parents, as part of their probe into a terrorism "hit list" found written in a notebook at the University of New South Wales.

On Friday, a terrorism charge was dropped against the notebook's owner Mohamed Nizamdeen, as police conceded it was "likely" he was not the author of the manifest, which made reference to former Prime Minister Malcolm Turnbull, former Foreign Minister Julie Bishop and the Sydney Opera House.

Mohamed Nizamdeen was released from custody after police declared he was "likely" not the author of the terror hit list. Photo: Supplied

Nizamdeen had spent more than a month behind bars in Goulburn's Supermax jail, after the notebook was found inside his desk at the University by a co-worker.

It's understood police are now investigating whether Nizamdeen was "set up".

Arsalan Khawaja (left) poses with his brother cricketer Usman Khawaja and The Ashes trophy. Photo: Facebook

Arsalan Khawaja works at the university with Nizamdeen, although it's not clear whether he was the person who provided police with their initial tip-off.

His father Tariq Khawaja confirmed to Ten News that police arrived at the family's Westmead home this week, armed with a search warrant.

"They have their job to do. There's nothing to worry about," he said.

Father Tariq Khawaja at his Sydney home on Saturday. Photo: Ten News

Asked whether his son had any connection to the notebook, Mr Khawaja replied: "He is his colleague. He works with him. I have no idea about this. Sorry, I can't discuss this."

It's understood police seized material containing Arsalan Khawaja's handwriting during the search warrant, with the intention of comparing it to the notebook.

Arsalan Khawaja in a photo on his social media account. Photo: Facebook

No charges have been laid against Arsalan Khawaja, although the police investigation is ongoing.

Mohamed Nizamdeen's lawyer said his client planned to seek legal costs in the Supreme Court and planned to sue NSW Police over the arrest.

"What authorities have done to this young man is absolutely unforgivable", Moustafa Khier told reporters on Friday.

However, police refused to apologise, declaring officers can never be complacent.

"I think those that were involved in the production and manufacture of these documents are the ones that have had an impact on Mr Nizamdeen", said NSW Police Assistant Commissioner Mick Willing.