In another curious wrinkle in the case, Israeli TV reported that Zygier had worked as a clerk in the international business department of one of Israel’s most prestigious law firms, Herzog Fox & Neeman. The firm is partially owned by Israel’s Justice Minister, Yaakov Neeman.

When asked in parliament about the Australian TV report on Tuesday, Neeman said he knew nothing of the case but said any allegations, if true, should be investigated.

Australian legislators demanded answers Wednesday about the suspicious death.

Among the lawmakers demanding clarifications was shadow Foreign Affairs Minister Julie Bishop, who told ABC that she wanted to know why details of the case were being censored in Israel. She said she would raise the issue with the Israeli Embassy.

Information about the case emerged briefly in June 2010, when the Israeli news site Ynet reported on the existence of a prisoner — identified only as Prisoner X — whose crimes were unknown. The report was mysteriously removed from the site shortly after it was posted, apparently under pressure from Israel’s military censor. The censor has authority to block or delete reports deemed threatening to national security.

Ynet then reported on Dec. 27, 2010, that a prisoner had committed suicide while in solitary confinement two weeks earlier. That report was also quickly removed.

The Israeli censor’s office declined comment.

The ABC reported that Zygier moved from Australia to Israel in 2000, was 34, was married to an Israeli woman and was the father of two young children. It reported that his incarceration was top secret but did not say why he had been arrested.

It said he hanged himself in a cell that had been specially designed for Yigal Amir, the Jewish ultranationalist who in 1995 assassinated then-Prime Minister Yitzhak Rabin.

Australia’s foreign affairs department would not comment on what it described as the ABC’s ‘‘speculation’’ on Allen’s links to Mossad.

Israeli TV speculated that Zygier was imprisoned after committing some kind of act of treason.

Israeli Channel 10 TV reported that in 2009, Australian intelligence officers interrogated Zygier when he was in Australia, questioning him about trips to Iran, Lebanon and Syria.

The TV report alleged that the matter was leaked to an Australian reporter, who phoned Zygier and questioned him about his alleged Mossad links. He reportedly denied the allegations. The TV report said some time later, he was put in jail in Israel, and six months later he was found dead in his cell.

In Israel, media were prevented from reporting many details of the Zygier case because of a court-imposed gag order.

A death notice published online from December 2010 announced the funeral for Ben Zygier. He is listed as the son of Geoffrey Zygier, the executive director of the B'nai B'rith Anti-Defamation Commission based in Melbourne.

Zygier’s father and his uncle, Willy Zygier, declined to comment on Thursday.

This is not the first alleged case of Israeli espionage involving an Australian passport. In May 2010, Australia ordered the expulsion of an Israeli diplomat after investigators concluded Israel was responsible for forging four Australian passports used by those responsible for the 2010 killing of a Hamas operative in Dubai.

At the time, Australia’s then-Foreign Minister Smith said Israel had previously forged other Australian travel documents. He did not elaborate, but said the 2010 transgression breached ‘‘confidential undertakings’’ between the two countries that have stood for several years.

The affair caused strains in an otherwise very close relationship between the two countries.

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