'Violent acts' foiled by Australian raids, 15 arrested

Australian authorities have carried out its largest ever "counter-terrorism" raids, arresting 15 people to stop an alleged plot by supporters of the Islamic State to carry out "demonstration killings" in public.

A pre-dawn operation was carried out across Sydney and Brisbane by more than 800 officers acting on some 25 search warrants.

The raids, which spanned multiple suburbs, came barely a week after Australia boosted the terror threat level to "high" for the first time in a decade, on growing concern about armed members of ISIL returning from fighting in Iraq and Syria.

"Police believe that this group that we have executed this operation on today had the intention and had started to carry out planning to commit violent acts here in Australia," authorities said. "Those violent acts particularly related to random acts against members of the public."

Reports suggest that the plan was to kidnap someone from the street and behead them while filming it.

The Australian government believes up to 60 Australians are fighting alongside ISIL, while another 100 were actively working to support the movement at home.

The latest raids followed the arrests of two people last week in Brisbane who were charged with allegedly recruiting, funding and sending self-declared jihadist fighters to Syria.