JERUSALEM: Recriminations grew in Israel on Thursday as more details emerged about the mysterious life and death of a prisoner held in top-secret who was believed to be an Australian-Israeli spying for Mossad.

As Israel finally admitted it had held a man with dual nationality in solitary confinement on security grounds who later committed suicide, a lawyer who met with him just days earlier said there was no indication the prisoner was planning to take his own life.

Prisoner X, who was identified by Australian media as Mossad agent Ben Zygier, is now known to have died in December 2010 while being held in Ayalon prison in Ramle near Tel Aviv in a case which Israel went to extreme lengths to cover up.

But given that key details of the case including the reason for his arrest and the circumstances of his apparent suicide are covered by a strict gag order, the answers may remain elusive.

"When I saw him, there was nothing to indicate he was going to commit suicide," said human rights lawyer Avigdor Feldman who met Zygier days before he was found hanged in his cell, which was under 24-hour surveillance.

Speaking to army radio, Feldman said he had met Zygier to offer him advice ahead of his trial as talks were under way over a plea bargain.

"He appeared rational, focused, he spoke clearly about the issue and didn't exude any sense of self-pity," Feldman said, expressing surprise that a prisoner who was being held in "a cell which was being monitored and checked 24-hours a day, could manage to commit suicide by hanging himself."

Until Wednesday night, Israel imposed a complete media blackout on the details of the case, but after easing the restrictions, the justice ministry admitted jailing a man on security grounds who took his life in December 2010.

It said an inquest into his death had rendered a verdict of suicide just six weeks ago.

But other details of the case remained under a gag order, leaving what commentators said was a growing list of "numerous and disturbing questions."

"Was there an attempt here by the relevant agencies, including the attorney general and the law enforcement organisations, to whitewash the affair and prevent an external investigation into the circumstances of his death?" asked Shimon Shiffer in the top-selling Yediot Aharonot.

Israel's attempts to suppress the story after it had already made headlines across the world "portrays our decision-makers as an illiterate band of mafiosos protecting narrow interests and looking to whitewash rather than protecting the security of the State of Israel," he said.

"The negligence is so outrageous that an investigation is needed to disprove it, along with the other alternative -- that someone pushed Zygier to his death, psychologically if not physically" wrote Amir Oren in the leftleaning Haaretz.

Senior political officials quoted by Yediot admitted Israel had made a big mistake in trying to bury the story. "There was a lot of panic here and a total lack of understanding of how the media operates in the Internet age," said one.

"Israel made a terrible mistake when it tried to prevent publication of the story in Israel after it was released in Australia," said another. "We only magnified the story and significantly exacerbated the damage done to Israel's image."

In Australia, Foreign Minister Bob Carr told a parliamentary committee the government had been informed in February 2010 through intelligence channels that Israel had detained a dual Australian-Israeli citizen.

He said Canberra would decide how to proceed after he had received a full report into the handling of the case.

The story first emerged in June 2010 when Israel's Ynet news website briefly ran a report about a prisoner being held in top secret conditions whose identity and alleged crime were not even known to his jailers.

The story was quickly taken offline and a complete media blackout imposed, but it resurfaced on Tuesday with the ABC report.

The sweeping gag order was slightly eased after three MPs used their immunity to raise the issue in parliament, effectively sidestepping the censor.

The Sydney Morning Herald said Zygier was being investigated by ASIS, Australia's overseas intelligence agency which suspected him of using his Australian passport to spy for Israel.