A man has been arrested in Sydney’s south-west over suspected terrorist activity.

The 21-year-old Riverwood man is expected to be charged for three offences, including carrying out acts in preparation for a possible terrorist attack.

Police say he pledged allegiance to Islamic State, created and posted extremist material online, actively tried to influence teenagers to adopt and act on his views, and downloaded a document about basic weapons and tactics.

NSW Police Assistant Commissioner Mark Walton tells Ben Fordham they have been investigating the man for six months.

“We’d been monitoring his activity and it got to a point where we knew we needed to act to prevent and disrupt him.”

Click PLAY below to hear the full interview