The gathering had been endeavoring to source a self loading rifle to murder whatever number individuals as could be expected under the circumstances in a swarmed place, experts said.
The suspects – matured 21, 26 and 30 – were purportedly motivated by the Islamic State gathering.
There was no continuous risk to general society, said Chief Commissioner Graham Ashton.
Mr Ashton said the men had not settled on an area for the supposed assault, yet their arranging had "heightened" lately.
"They were surely taking a gander at a position of mass social affair, where there would be swarms, since they were endeavoring to center around attempting to have a place where they could kill whatever number individuals as could be expected under the circumstances," he told journalists on Tuesday.
Prior this month, a blade using aggressor killed one man and harmed two others in Melbourne in what police said was a dread assault.
Mr Ashton said the suspects captured on Tuesday had moved toward becoming "more invigorated" in the previous week, however it was indistinct whether this was because of expanded open dialog about psychological warfare.