Al Qaeda's leader Osama Bin Laden could be seriously ill or dead, said an Australian terrorism expert Monday.

Australian Broadcasting Corporation radio quoted Clive Williams from Sydney-based Macquarie University as saying that he has seen evidence to support the theory that Bin Laden died of massive organ failure in April last year.

Williams said Ayman al Zawahiri, Bin Laden's deputy, has been making all statements on behalf of Al Qaeda for around a year.

But he said it may be impossible to ever prove if Bin Laden is dead.

"It's hard to prove or disprove these things because there hasn 't really been anything that allows you to make a judgment one way or the other," he said.

"But it does seem strange that Zawahiri has been making all of the statements since then, and nothing has been heard from Bin Laden since, I think, December of the year before," he said.

"I suppose there's a degree of satisfaction from a counter- terrorism point of view that he's no longer around," he added.

Williams continued to say it would not make much difference if Bin Laden is dead or not, as "the things he said and the things he stood for are probably the more important legacy and will motivate people to engage in jihad fighting into the future."

Source: Xinhua