A plan by ISIS to "gruesomely" execute a randomly selected member of the public in Sydney was thwarted by police on Thursday, according to Australian Prime Minister Tony Abbott.

More than eight hundred police officers carried out raids on more than a dozen properties throughout Sydney on Thursday, arresting 15 suspects. An arrest warrant was also issued for Mohammad Ali Baryalei, a former bouncer believed to be Australia's highest ranking member of ISIS.

The plot in Australia reportedly included plans to behead a member of the public as part of a "demonstration killing."

"That's the intelligence we received," Abbott told reporters, according to the Associated Press. "The exhortations — quite direct exhortations — were coming from an Australian who is apparently quite senior in ISIL to networks of support back in Australia to conduct demonstration killings here in this country."

About 60 Australians are reportedly fighting with the Islamic State group in Syria and Iraq, not including 15 Australians—including two suicide bombers—who have already been killed. Dozens more ISIS-supporters are thought by police to be in Australia, working on recruitment for the militant group.

From the Associated Press:

The arrests come just days after the country raised its terror warning to the second-highest level in response to the domestic threat posed by supporters of the Islamic State group.

"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," said Colvin, who is also the acting Federal Police Commissioner. "Those violent acts particularly related to random acts against members of the public. So what we saw today and the operation that continues was very much about police disrupting the potential for violence against the Australian community at the earliest possible opportunity."

Exact details of the attack were not released, though New South Wales Police Commissioner Andrew Scipione described the threat as "at a very high level."

[Image via AP]