The president of a Parramatta mosque that was raided after the terrorism-linked shooting of a NSW police employee has denied any connections with teenage gunman Farhad Jabar Khalil Mohammad.
"We don't know the boy, or where he lived because he's not a regular person in the congregation," Neil El-Kadomi told the ABC's 7.30 program.
Radical Islamic group Hizb ut-Tahrir has also denied links to the teenage killer.
The 7.30 program reported on Monday that it's believed a small group of men at Parramatta Mosque encouraged the 15-year-old to attack.
The teen reportedly attended a lecture by the group at Parramatta Mosque on Friday, shortly before gunning down veteran police accountant Curtis Cheng, 58, as he left work at the Parramatta police headquarters.
Mr El-Kadomi said if anybody was suspected of using the mosque to radicalise others, he would tell police immediately.
"I don't hesitate," he said.
"Going to the police straight away better than to be sorry later."
Hizb ut-Tahrir says claims that the teen was affiliated with the group are "groundless and absurd".
"Hizb ut-Tahrir's position on the use of violence as a means for political change or expressing political grievance is also extremely well known," the group told AAP on Monday.
"Actions like the Parramatta shooting are plainly wrong."
Claims that the teen had been radicalised drew condemnation of extremist organisations, including from Labor leader Bill Shorten who likened radicals to pedophiles.
"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.
"These organisations preying upon young people are a sort of political or a terrorist version of pedophiles who prey upon young people."
The consensus among politicians, community and police has been that early intervention is the key to protecting against radicalisation.
Prime Minister Malcolm Turnbull told reporters in regional Victoria that members of the community need to be aware of how 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 said.
He says it's still unclear whether the boy was acting as a "lone wolf" who carried out the violent act outside of a group command structure.
Police have been told to maintain heightened vigilance against threats of violence, including revenge attacks, but not to overreact.
The Australian Defence League used social media over the weekend to call for "eye for an eye" attacks against mosques and imams.
NSW Police Deputy Commissioner Nick Kaldas says Friday's tragic shooting can't be allowed to divide the community.
"The bad guys win if we are divided, if we stop living our normal lives, if we don't do what we want to do," he said.
