Counterterrorism police are investigating a disturbance outside a Perth mosque overnight and the discovery of white powder, described as "non-suspicious", on the footpath outside.
Police said they received a report of a melee outside the Perth Mosque on William Street in Northbridge about 1am.
"Officers attended and identified that a non-suspicious substance had been placed on the front doorstep," police said in a statement.
The State Security Investigation Unit, which handles the most serious security threats including suspected terrorism and extremism, is investigating the incident.
Police commissioner Col Blanch said the substance was a white powder.
It comes a day after 20-year-old Jayson Michaels from Bindoon, on Perth's rural outskirts, was charged with preparing an act of terrorism, the first charge of its kind to be laid in WA.
It is also less than a month since Liam Hall, 31, was charged with engaging in a terrorist act after allegedly throwing a homemade bomb into a crowd at an Invasion Day rally in Perth's CBD.
Police seized guns and knives from Mr Michaels's home in Bindoon, about 65 kilometres north-east of Perth, and he appeared in the Perth Magistrates Court yesterday facing five charges.
Senior government leaders, including the premier, are at Perth Mosque today to meet with community leaders in the wake of the alleged terror plot's discovery.
Commissioner Blanch said a "white inert powder" had been found on the footpath outside the Perth Mosque.
CCTV footage is being analysed by police as part of their investigation.
"We don't know if it was in fact targeted at the mosque, but certainly given the location we are doing an investigation," Commissioner Blanch said.
He did not provide further details on the nature of the disturbance.
The commissioner also provided an update on the investigation into Mr Michael and said detectives were working to establish whether he had been radicalised by individuals in his "sphere of influence".
He said the man's parents, with whom he lived in the small semi-rural community about an hours' drive from Perth, were currently cooperating with police.
Commissioner Blanch said the investigation had focused on a white supremacy group chat on an encrypted Telegram service, which included a group of Australians and international members.
Police did not currently believe the group was linked to established white supremacy groups like the National Socialist Network (NSN), which last year disbanded after the passage of anti-hate speech laws through federal parliament.
"All we can see is a group of like-minded, meaning white supremacist, groups talking about their hate for other people in our community," he said.
"Early indications are there's no hierarchy, there's no structure, there's no organisation."
He said Mr Michaels was the only West Australian who had been identified but work was underway to identify others.
"That's the work that's being undertaken now as part of the joint counterterrorism team investigation, is in fact to obtain all of the messages, extract all those messages and go through them one by one," he said.
"So if you know that you have been on that message group, if you are someone that has participated in those conversations, you can expect a knock on your door, and it won't be a quiet knock, let's put it that way."
Perth Mosque Imam Sheikh Shakib Mohammad said divisive rhetoric by politicians and the broader community had been "unhelpful".
He particularly singled out Pauline Hanson's comments asking whether there were any "good Muslims" in the context of a discussion on the return to Australia of wives and children of Islamic State militants currently stranded in Syria.
The comments have been widely condemned as inflammatory, divisive and hateful.
Imam Mohammed said his congregation was made up of everyday Australians, including doctors, nurses, lawyers, teachers and business owners, and this kind of "divisive rhetoric" had to stop.
"How on earth can you have a certain politician that demonises an entire faith group?" he asked.
"Islamophobia has become so normalised it's become mainstream.
"When we have good people that remain silent, when you know people are being attacked … whether it be the schoolgirl on the bus that's wearing a headscarf who's visibly Muslim … vulnerable people like that schoolgirl on the bus [are] going to face the brunt of this reckless language."
