The flag held by hostages against the window of a Sydney cafe in television pictures beamed around the world is not directly associated with the Islamic State group, but has been co-opted by other jihadist organizations, Australian media reported Monday. 

The white Arabic writing on the black flag is the Shahada, or Islamic declaration of faith. Translated, the statement means "There is no God but Allah and Muhammad is His messenger." It is considered the first of Islam's five pillars of faith, and is similar to the Lord's Prayer in Christianity. It is pervasive throughout Islamic culture, including the green flag of Saudi Arabia. Jihadis have expropriated the Shahada in their own black flag.

"It is not the Islamic State flag per se," Ben MacQueen, a senior politics lecturer at Monash University in Melbourne, told the Sydney Morning Herald. "It has been used in recent times, for example, by Chechen groups."

Australian authorities have repeatedly warned about the threat posed by Islamic State, better known as ISIS. Earlier this week, the government estimated that approximately 70 Australians are currently fighting with the terror group in Iraq and Syria, while another 20 are believed to have been killed in action and 20 others are believed to have returned home. 

In September, police made over a dozen separate raids in the suburbs of three cities, including Sydney, in an effort to break up a plot to behead a randomly selected person on a city street and record it. Days later, Australian intelligence agencies said they had uncovered an ISIS plot to attack the country's parliament. 

Terrorism experts said Monday that the flag used by the unidentified hostage-taker neither confirms nor rules out an association with ISIS. 

"Getting hold of an [ISIS] flag would be quite difficult," Greg Barton of Monash University in Melbourne told the Sydney Morning Herald. "and people will make do with what they have got."

MacQueen concurred, suggesting that the hostages were "maybe young guys, maybe not savvy, they've got their hands on a bit of paraphernalia to suggest they have aligned themselves with the IS. If this was centrally organized from Syria or Iraq they would not be using that flag."

The Associated Press contributed to this report.

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