Updated

Police on Thursday cautioned Australians to be vigilant after an Al Qaeda-linked online magazine published a picture of Sydney's iconic Opera House, and expressed concern about its influence on the local Islamic community.

"If you thought the terrorism risk had diminished and gone away, then you are wrong," said Andrew Scipione, head of state police in New South Wales, of which Sydney is the capital.

"We should never become complacent when it comes to preventing acts of terrorism -- so it is a really important wake-up call for us all," he said.

Police are unclear about the significance of the Sydney Opera House photograph appearing in the latest issue of Inspire, an English-language online magazine published by associates of Al Qaeda in the Arabian Peninsula. The picture was carried without any comment or reference point.

The photo came to police attention after it was posted earlier this week, and local media reported on it Thursday. The magazine cover features a picture of late Al Qaeda leader Usama Bin Laden.

The Opera House picture is on page 35 of the 61-page publication and serves as the cover of a section that includes lessons on how to use an AK-47 rifle and how to make bombs. The image is accompanied with the title "Open Source Jihad."

Below it are the words, "In this section: Training with AK (Part 3) Making Acetone Peroxide."

Australia, an isolated island continent, has been largely untouched by terrorism, unlike other countries in the Asia-Pacific region, especially neighboring Indonesia. Bombings on its tourist island of Bali in 2002 killed 202 people, 88 of them Australian.

New South Wales counter-terrorism chief Peter Dein said there was no evidence the Sydney Harbor-side Opera House was under threat and speculated the publishers might have just wanted to spread fear.

"It could simply be the fact that it's an icon that is well known around the Western world and may not really have any relevance that it is in Sydney," he told reporters.

He said he was more worried about the influence of the magazine's extremist rhetoric on Australia's "vulnerable" Islamic community because US-born Yemeni cleric Anwar al-Awlaki was behind the literature.

Al-Awlaki has a following among English speakers in the United States and Britain based on video sermons that discuss foreign policy and poor job prospects for young Muslims. He reportedly delivered a video-linked sermon to young Australians in western Sydney's Lakemba mosque last year.

It had been well publicized that there were about 100 people in Australia affiliated with terrorists, Dein said.

Last December, three Australians of Somali and Lebanese origin were convicted of plotting a suicide attack against a Sydney army base.

Australia's terrorist alert level remains at medium, which means an attack could occur, and will not be changed because of the publication, said Attorney General Robert McClelland.