Kuwaiti newspaper said Ben Zygier had provided the authorities in Dubai with details about the secret killing in 2010 in exchange for protection from Israel.
The Australian-Israeli man recently identified as Prisoner X -- found dead in 2010 in a maximum-security prison cell -- may have been involved in the assassination of a Hamas leader that year, an episode that was among the most embarrassing in the history of the Israeli intelligence agency, the Mossad.
The Kuwaiti newspaper Al Jarida reported Thursday that the prisoner, Ben Zygier, who immigrated to Israel from Australia and apparently spent a decade working for the Mossad, was among the 26 suspects in the assassination plot, in which Mahmoud al-Mabhouh, a Hamas official, was drugged and suffocated in his hotel room in Dubai.
Al Jarida, a liberal opposition newspaper, said Mr. Zygier had provided the authorities in Dubai with "names and pictures and accurate details" in exchange for protection, but Israel kidnapped him from a hiding place and imprisoned him on charges of treason about a month after the operation on Jan. 19, 2010.
The Dubai plot, for which Israel has never acknowledged responsibility, led to diplomatic sanctions against Israel because fake passports from Europe and Australia were used. Australian journalists reported Thursday that Mr. Zygier, one of several people under investigation by the Australian intelligence service on suspicion of passport fraud, was arrested just before he was set to disclose Israeli secrets about the passports to the Australian government or the news media.
The reports quoted a security official with knowledge of the case as saying that Mr. Zygier "may well have been about to blow the whistle, but he never got the chance."
The Israeli prime minister's office and the Justice Ministry declined to comment on the emerging details in a case that has dominated the news here for days, more than two years after what appeared to be the suicide of a man known only as Prisoner X was revealed in local news reports that the government immediately quashed.
Politicians, journalists and human rights advocates have questioned the appropriateness of Mr. Zygier's secret detention; the circumstances of his death by hanging, which was ruled a suicide despite his cell having been under constant surveillance; and the extraordinary court order that banned local reporting on the entire episode.
"The Prisoner X affair is a classic story of Israeli failure," read the headline over a column by Amir Oren in the left-leaning daily newspaper Haaretz. "The most sensitive agencies aren't functioning," Mr. Oren wrote. "In its 65th year, the State of Israel still doesn't control the basics."
The news blackout was only partially lifted Wednesday evening and may have done more damage than it prevented. Much of the outrage revolved around reports, none of them true, that Prisoner X was denied visitors and that a lawyer, his family and the Australian Embassy were never informed of his detention.
On Thursday, a lawyer hired by Mr. Zygier's family said that he had met with him a day or two before his death to discuss a plea bargain. "The crimes he was suspected of were serious," the lawyer, Avigdor Feldman, told Channel 10 News in Israel, refusing to elaborate. "He denied the charges," Mr. Feldman added.
In a separate interview with Army Radio in Israel, Mr. Feldman said that Mr. Zygier, a lawyer who worked for a year at a prominent Israeli firm, "had been informed that he could very likely expect to be sentenced to an extremely lengthy prison term and to be shunned by his family -- and this affects a person's soul."
It is unclear how a Mossad agent who had revealed details to a foreign government about an assassination, particularly one as fraught as the Mabhouh affair, would be eligible for a plea bargain. But if the secrets had not yet been shared, and they were limited to information regarding passport fraud rather than murder, a reduction in charges might be more realistic, experts said.
Mr. Feldman said that Mr. Zygier, who was 34 and whose second child, a girl, was born four days before his death, had not shown any suicidal signs. "He sounded rational and focused, and he spoke to the point," the lawyer told Army Radio. "He did not display any special feeling of self-pity."
Mr. Feldman was one of many in Israel who called for further inquiry into Mr. Zygier's death. "Those responsible for him should have taken clear steps to watch over him," Mr. Feldman said.
In Australia on Thursday, the foreign minister revealed that his government had learned of Mr. Zygier's detention on Feb. 24, 2010, contrary to an earlier ministry statement that it had been unaware until the family requested repatriation of his remains in late December. The minister, Bob Carr, declined to say whether the government knew the specific charges, saying only that officials were informed that Mr. Zygier had been detained "in relation to a serious offense under Israeli national security legislation."
Australia was one of several countries whose relations with Israel were strained by the revelations made by Dubai authorities after the assassination of Mr. Mabhouh, a founder of Hamas's military wing, who played a role in the kidnapping and killing of two Israeli soldiers in 1989 and who helped supply Hamas with weapons from Iran.
In a confidential diplomatic cable published by WikiLeaks, the Australian Foreign Ministry told the U.S. Embassy in Canberra that the Dubai affair had made a coming vote at the United Nations more complicated. "Australian officials are 'furious' all the way up the chain of command," it said. "In the wake of revelations from Dubai, the government is in no hurry to reassure Israel of its support."
The cable was dated Feb. 25 -- one day after Mr. Carr said Australia was notified of Mr. Zygier's detention.
Gad Shimron, a former Mossad agent who wrote a book about the agency, described Mr. Zygier's case as "so unusual and so extraordinary," but not unique.
"Throughout the Mossad's history there are plenty of stories about people who at one point or another behaved in a way that is so bluntly different than the James Bond kind of manner they were expected to be," Mr. Shimron said in a radio interview.