Dr Gunaratna, who is based at St Andrews University, Fife, said: 'From the style of that message and the way in which it's been issued it's very clear that this is from Osama bin Laden himself.
Dr Gunaratna said that the message, which featured prominently on the website, had bin Laden's 'signature all over it' but did not state that he was its author because 'it is important for al Qaeda to maintain ambiguity about whether he is alive or dead'.
He went on: 'It's in the interests of the Jihad campaign to keep people guessing about whether Osama bin Laden is still living.
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