Authorities need to counter the sleek propaganda of Islamic extremists with facts, a key Muslim leader says.

Two brothers, aged 16 and 17, were intercepted at Sydney airport on Friday night after a luggage search raised suspicions they intended to join the conflict in the Middle East.

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Dr Jamal Rifi is relieved Customs officers were able to intervene but despairs at the “toxic social media environment” that continues to lure youngsters into a trap.

“That is the question – why such sleek propaganda that is taking place is not being counteracted by another, you know, fact finding,” he told ABC TV.

Dr Rifi called for more government support to help communities combat radical ideology.

An Islamic State recruit declared a “white jihadi” by the UK press in December has been identified as an 18-year-old Melbourne boy called “Jake” by Fairfax Media.

He went to Craigieburn Secondary College and was a good student before he dropped out mid last year after converting to Islam and then headed to the Middle East to join IS.

Meanwhile Immigration Minister Peter Dutton said the western Sydney brothers, who were stopped at the airport on Friday night, will be put on to a watch list.

“The authorities will be working really hard with the families,” he told the Seven Network.

“On the advice I’ve got, the mum and dad had no knowledge of what was going on.”

Mr Dutton said the online “radicalisation” of Australian youth was a threat to society.

“We take it very, very seriously,” he said,

“It’s a warning message to a lot of parents, you work with your kids, understand what they are looking at online.”

Mr Dutton also praised the move by NSW correction authorities to ban terror suspects in maximum security prisons from communicating in Arabic.

“This is a really good move,” he said.

“We need to make sure authorities are on top of any threat.”