Firefighters and homeowners aren't the only ones keenly watching Australia's massive wildfires, responsible for killing at least 173 people in the southern part of the continent.

Terrorism experts suspect Muslim extremists are watching closely, too — and taking note of the devastation.

While Australian authorities have revealed no evidence linking the wildfires to extremists, terrorism experts say the large death toll, the huge swath of destruction and the massive financial blow to the country are proving to Islamic terrorists that arson can be a highly effective — and simple — tool of holy war.

In November, an extremist Web site called on Muslims to launch a "forest jihad" in Australia, Europe, Russia and the United States. The posting, which quoted imprisoned Al Qaeda terrorist Mustafa Setmariam Nasar, said setting forest fires was legal under "eye-for-an-eye" Islamic law.

"Scholars have justified chopping down and burning the infidels' forests when they do the same to our lands," the posting read.

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The author of the posting indicated that Nasar — also known as Abu Musab Al-Suri — was urging terrorists to use sulfuric acid or gasoline to start the fires.

"Forest fires track well with the latest discussion trends seen in the Al Qaeda forums — easy to do, big impact, low security risk, high media coverage," said Al Qaeda expert Jarret Brachman.

"We've seen these kinds of appeals for action, be it setting fire to forests in Australia, to creating oil slicks on mountain roads in Europe, to poisoning water supplies and driving buses off bridges in the United States.

"The fact is that the Al Qaeda ideology is starting to branch out to more of an 'anyone, anywhere, anytime, anyhow' approach."

Brachman, author of "Global Jihadism: Theory and Practice," said "forest jihad" fits well in the growing interest among terrorists to establish "Al Qaeda armies of one."

"Could [militants] do this? Yes," said Steve Emerson, executive director of The Investigative Project on Terrorism. "It wouldn't be difficult, in the same way that terrorists could poison stored food supplies."

Perhaps more troubling, Emerson said, is that there is very little authorities can do to prevent terrorists from setting deadly wildfires.

"It would be absolutely impossible to protect against," he said. "Airport parameters are hard enough to protect. Imagine trying to protect something 100,000 times as big."

Neil Livingstone, chairman and CEO of Executive Action LLC, an international consulting firm, said terrorists could claim responsibility for the Australian inferno even if they had nothing to do with it.

"That may be something that they try to do," Livingstone told FOXNews.com. "Terrorists may well try to pile on, if you will, and say this is their moving hand and that they have unseen agents that are responsible for this. But you can bet that would produce a hell of a backlash against the Muslim population in Australia."

If extremists did have had a hand in the wildfires, Emerson said, it would be "very disturbing."

"It would indicate a new area of jihadist attacks, that is, attacking natural resources," he said. "And given the devastation of these fires, it certainly could instill new terror ideas in other areas like the food supply chain or in the environmental realm."

Nonetheless, he said, the majority of terrorists are likely seeking ways to create the most destruction with the least amount of effort. A wildfire doesn't yield "as much fruit" as an inner-city bombing, he said.

But Brachman said the "Al Qaeda armies of one" approach has several benefits for terrorists, including more overall acts of violence and additional opportunities to become involved in new geographical areas. It also means less operational control for Al Qaeda's senior commanders, he said.

"We're definitely going to see more of calls for these kinds of operations in the future," he said. "The question that American security professionals and first responders will have to wrestle with is whether anyone will be answering these calls."