Australian police are investigating claims a Sydney bookshop has been selling extremist Muslim books.
One of the books is said to discuss suicide bombing techniques
One of those under scrutiny is said to have been endorsed by Osama Bin Laden.
New South Wales police commissioner Ken Moroney said police needed to determine whether any offence to incite violence or hatred had been committed.
The owners of the shop - the Islamic Bookstore - have said they will issue a statement on the issue after speaking to their lawyers.
Muslim leaders in Australia say they strongly condemn such literature.
According to Sydney's Daily Telegraph newspaper, the Islamic Bookstore has been stocking a book entitled Defence of the Muslim Lands, which has an endorsement by al-Qaeda leader Osama Bin Laden on the cover.
The book discusses the effectiveness of suicide bombings, as well as details of various bombing techniques.
Other controversial books were also reportedly found at the store - including Join the Caravan, which poses the question: "For how long will the believing youths be held back and restrained from jihad?"
Books with similar content were found in other Sydney stores, the Daily Telegraph alleges.
Police Commissioner Ken Moroney said legal advice would be needed to determine whether the retailers, publishers and authors of the literature had committed an offence.
"Clearly it is an offence to incite people to commit a range of offences," he said. "Personally, I regard the material as offensive at a minimum."
A prominent Muslim leader, Australian Islamic Friendship Association president Keysar Trad, said he was "concerned that such books were readily available".
"I don't know whether the bookshop owners are aware of what's inside these books, but there should be a lot more vigilance," he said.
But the chairman of the Supreme Islamic Council of New South Wales, Gabr Elgafi, said that censorship was not the answer to banishing violence and hatred.
"I think for people to talk or write is a good thing," he told ABC News.
"To muzzle people, I don't think it's a good idea. We don't encourage hate - we actually oppose hate. But we have to let people talk."
Following the recent bombings in London, Australian Prime Minister John Howard, a staunch ally of the US-led war on terrorism, warned that his own country was not immune to similar suicide attacks.
Australia has never suffered a major terror at home, but its embassy in Jakarta was bombed in 2004 and 88 Australians were killed in the 2002 Bali bombings.
Both attacks have been blamed on the regional Islamic militant group Jemaah Islamiah.