Commenting on a YouTube video of al-Qaeda bombing a Yemen hospital, the Panania man, who was arrested at Sydney Airport on Thursday allegedly trying to join Islamic State, said he abhorred violence.

"The people who did this are not 'muslim' and they have nothing to do with islam, we are forbidden to kill innocent people," he wrote. "Stop blaming islam when its these crazy brainwashed fools that are doing these things."???

But, three weeks later, he was singing the praises of Sheikh Anwar al-Awlaki, an al-Qaeda attack planner who was killed by a US drone strike in 2011.

"Words of gold!!!!" he posted beneath a now-removed interview of the Yemeni-American cleric.

After watching a video that was critical of Islamic State, he posted: "ISIS all the way!!"

Police allege Mr Taleb, 22, was radicalised through online communications before he took a taxi to Sydney Airport on Thursday morning, allegedly intending to travel to the Syrian war zone.

He was allegedly going to buy a one-way ticket to Turkey or Lebanon at the airport, NSW Police deputy commissioner Dave Hudson said.

Wearing track suit pants, a patterned beanie and a spray jacket, Mr Taleb was arrested by plain-clothed police officers on the airport's outdoor concourse at about 10am.

Mr Hudson wouldn't say if police followed the man from his family's bungalow in south-west Sydney to the airport, however the Joint Counter-Terrorism Team had been monitoring him closely since January.

"Some of the communications that this particular individual has been communicating has caused us concern and increased our focus upon him," he said.

He wouldn't divulge who Mr Taleb had communicated with online but said that police believe he was largely acting alone.

"There needs to be a certain intent for the person themselves that they go looking for certain information that changes their way of thinking," he said. "People try and source that material themselves rather than being approached."

Just two weeks ago, he was charged with stalking or intimidating an older female relative he was living with and an AVO was implemented.

He was also charged last October with assaulting a young male relative at home one night.

Detectives removed a computer and several bags of evidence from the home on Thursday as Mr Taleb was questioned at Mascot police station.

On Thursday evening, police said he had been charged with one count of "Preparations for incursions into foreign countries for purpose of engaging in hostile activities", which has a maximum penalty of life imprisonment.

More than 200 Australians have left to fight for terrorist groups including IS in Syria since civil war broke out in 2012. Hundreds more have been stopped at airports.

Mr Hudson said he believed it was better to stop the man rather than allow him to leave.

"There's a responsibility on law enforcement in controlling these situations at the point we can control it. We took the decision that it was more preferable that we acted this morning rather than allowing someone to leave the country and return at a later date."

Mr Taleb will appear in Central Local Court on Friday.