Terrorist organisations are like pedophiles in the way they prey upon vulnerable young people, Opposition Leader Bill Shorten says.
His comment comes after reports the 15-year-old boy who shot dead a NSW police accountant on Friday had earlier attended a lecture by extremist group Hizb ut-Tahrir at the Parramatta mosque.
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Farhad Jabar Khalil Mohammad was then shot and killed by special constables returning fire.
Mr Shorten wouldn't speculate on police investigations of the shooting or alleged extremist involvement on Monday, but said groups that filled the heads of vulnerable young people with "murderous crazy nonsense" were breaching their social contract with Australians.
"Labor has no time for any organisation found to be fomenting this dangerous, crazy rubbish, which is preying upon teenagers with such dreadful, tragic consequences," he told reporters in Sydney on Monday.
"These organisations preying upon young people are a sort of political or a terrorist version of pedophiles who prey upon young people."
Parents should keep check of kids: PM
The prime minister says it's too early to comment on whether the Parramatta police shooter was a lone wolf, urging parents to keep check of their children.
Prime Minister Malcolm Turnbull has urged parents to keep tabs on what their children are up, to head off the risk of exposure to terrorist groups like Islamic State.
Mr Turnbull said it's too early to say whether Parramatta police shooter Farhad Jabar Khalil Mohammed was a "lone-wolf" - someone who carries out violent acts of terrorism outside of a group command structure.
"We all need to be aware of the way in which radicalisation can occur - communities at every level, families should be aware of what young people are doing, what influences are impacting on young people," he told reporters in regional Victoria on Monday.
Investigations into Friday's shooting death of a police accountant by Mohammad are continuing.
Mr Turnbull plans to speak on Monday with the family of worker Curtis Cheng.
"It's troubling and shocking that somebody as young as 15 would commit a crime like this - it is a doubly sickening crime for that reason," he said.
The prime minister said the internet was rapidly changing the dynamics of countering extremism, suggesting the government could learn from UK's experience.
"We have to constantly calibrate our response and learn from what we're doing, what works."
