As thousands of Australians took to the streets protesting against the American occupation of Iraq on the first anniversary of the invasion, the Australian government did not rule out the possibility that al-Qaeda chief Osama bin Laden's deputy, Ayman al-Zawahiri, visited the country in the 1990s.

Al-Zawahiri did not visit Australia under his own name or a known alias, said Australia's Federal Attorney-General Philip Ruddock.

"Now that doesn't mean to say that he may not have come under some other false documentation or some other alias that's not known to us," Ruddock said. "I suppose the only point I would make from the reports that we are now seeing is that if it were true, it would affirm once again the continuing interest that al-Qaeda has had in Australia over a long period of time."

Ruddock urged anyone with information about al-Zawahiri's reported visit to come forward.

Hamid Mir, a Pakistani journalist who was the first to interview bin Laden after the 9/11 attacks, told ABC TV that the al-Qaeda second-in-command had arrived in Australia on a false passport.

"He [al-Zawahiri] told me that in the early 1990s he travelled to New Zealand. He was there to meet some of his people, then he came to Australia, then from Australia he went to Indonesia. In those days, in early 1996, he was on a mission to organise his network all over the world," Mir said.

"He told me he stopped for a while in Darwin. He was... looking for help and collecting funds." 

Mir said al-Zawahiri also told him about nuclear weapons.

"Dr Ayman al-Zawahiri laughed and he said Mr Mir, if you have $30 million, go to the black market in Central Asia, contact any disgruntled Soviet scientist, and a lot of... smart briefcase bombs are available. They have contacted us, we sent our people to Moscow, to Tashkent, to other central Asian states and they negotiated, and we purchased some suitcase bombs," Mir said in the interview, which will be screened on Monday night.

The Weekend Australian newspaper also quoted Mir as saying from Islamabad on Friday that al-Zawahiri claimed to have visited Darwin some time between 1992 and 1996.

Mir said, "At that time [al-Zawahiri] was moving around the world as a businessman travelling on false passports, often using Christian names. He told me he stopped for a while in Darwin -- he was definitely organising his network, looking for help and collecting funds."

Mir said he has written about al-Zawahiri's claims, including his alleged Australian visit, in his forthcoming biography of bin Laden.

"Al Qaeda is not targeting only America -- it is also trying to target all countries, including Australia and Pakistan, who are partners of US in war against terrorism."

Meanwhile, Mohammad Nurul Huq, a representative of Darwin's Islamic community, has reportedly said that he has "not heard of Osama bin Laden's deputy" and is "uncertain if there is a record to determine if the man visited the city".

Before allowing a person in, "we make sure that who is he, his identity and if we are satisfied we allow him to stay here for a night. Mostly they don't stay in the mosque but sometime somebody needed it. But normally they come to the mosque, they pray, they go", he was quoted as saying.