The heads of two pigs have been found on stakes at the site of a proposed Islamic school in Sydney's south-west.
About 6am today, police were called to the site, on Cawdor Road, Camden, where they found the animal remains and a number of other items, a police spokesman said.
The pig heads had been "elevated off the ground" using stakes, he said.
An Australian flag was also strung up between the stakes, according to AAP.
The police spokesman would not say what the other items left at the site were.
He said he was not aware of any messages being left behind.
The Quranic Society's plan to build a primary and high school for 1200 students at the Camden site has sparked a strong backlash from residents.
This month about 1000 people attended a meeting to protest against the building of the school.
Police have conducted a forensic examination of the animal remains, but were appealing for witnesses or anyone with information to phone Camden police station or Crime Stoppers on 1800 333 000.
The police spokesman said he was not aware of any other similar incidents at the site.
Camden Council is expected to make a decision early next year on the society's proposal to build the school.
Quranic Society spokesman Jeremy Bingham slammed the act as "low'' and "hurtful''.
"It's not representative of anybody, of any Australian - there's nothing more un-Australian than exhibiting that kind of prejudice,'' he said.
In 2004, a severed pigs head had been similarly impaled in front of a muslim prayer centre in Annangrove, in Sydney's north-west, Mr Bingham said.
"This is just some imitative twerp copying what's been done before at Annangrove three or four years ago - it's just a copycat bit of nonsense,'' he said.
The "anti-social behaviour of just one individual'' would have no impact on the Quranic Society's bid to have the school approved, Mr Bingham said.
AAP reports: NSW Community Relations Commission chairman Stepan Kerkyasharian said today's "outrage" revealed what lay behind the opposition to the school.
"This insult and display of hatred is not something any fair-minded Australian would approve of," Mr Kerkyasharian said in a statement.
"The obsessive hatred of the mindless bigots who perpetrated this outrage is evidenced by their total disrespect of the ultimate symbol of our national pride, the Australian flag.
"Every Australian Muslim would be offended by such a display, especially one involving the Australian flag."
Mr Kerkyasharian said local residents with legitimate concerns about the impact of the development should condemn the action.
Camden Mayor Chris Patterson said the offensive protest was futile.
"The council will only and can only assess this DA (development application) on planning grounds, nothing else," Mr Patterson told Macquarie Radio.
"Anything like that which happened last night is not acceptable and will not influence council's decision."
The CRC has offered the council its assistance in resolving the community tension.