A convicted terrorist accessed information about executions, beheadings and torture online "almost immediately" after their release from jail.
The release of such offenders from Australian jails is chewing up a significant amount of police resources, Australian Federal Police Commissioner Reece Kershaw told Senate estimates on Monday morning.
Eighteen terrorist offenders are scheduled for release by 2026.
The threat of terrorism is increasingly worrying police as the country emerges from lockdown, with the relaxation of restrictions making it harder for officers to track potential offenders.
The amount of online activity during lockdown made it easier to radicalise young people, estimates hearings heard.
"Children as young as 13 years old - not even old enough to get their learners' driver's licence - are planning and negotiating with others online to carry out catastrophic terror attacks," Commissioner Kershaw said.
"Some of these youth feel isolated or do not feel like they belong, and so they retreat to the online world, looking to connect with someone, including [extremists]."
Australian Associated Press