Israel's parliament is to conduct what it called an "intensive" inquiry into the arrest and death of a jailed Australian-Israeli with Mossad links, a parliamentary spokesman said on Sunday.
"The intelligence subcommittee of the (Knesset) foreign affairs and defence committee decided to hold an intensive inquiry into all aspects of the affair of the prisoner found dead in his cell," the committee spokesman Asaf Doron said.
He gave no further details.
The decision followed days of media frenzy sparked by the exposure last week of the identity of the man known as Prisoner X -- an Australian immigrant called Ben Zygier who worked for Israel's Mossad spy agency.
According to a story broken last Tuesday by the Australian Broadcasting Corporation (ABC), Zygier was found hanged in his cell in Ayalon prison near Tel Aviv in December 2010, in a case Israel went to extreme lengths to cover up.
It imposed a total media blackout on the case but was forced to ease the restrictions after the story made headlines across the world, rendering the local gag order ineffective.
In his first comment on the affair, Prime Minister Benjamin Netanyahu said on Sunday that shining too much light on intelligence activities can "badly damage" state security.
"Overexposure of security and intelligence activities can damage, and damage badly, state security and that is why in every debate we must not underestimate the security interest," he said in remarks to the cabinet communicated by his office.
"In the reality in which Israel lives, it must be a central interest," he said in a thinly veiled criticism of media speculation as to what might have been Zygier's precise intelligence role and the nature of his alleged offence.
Netanyahu spoke shortly after Canberra said it was seeking answers over the circumstances of Zygier's death.
"I ask everyone: let the security forces continue to work quietly in order that we can carry on living in peace and security in Israel," he said.
"We need to ensure that we protect the normal working of our security branches," he added, expressing "complete trust" in Israel's security forces and legal system.
Australian Foreign Minister Bob Carr said his office was preparing a report looking at all communications between Australia and Israel, including between its security agencies.
"We have asked the Israeli government for a contribution to that report," Carr told reporters. "We want to give them an opportunity to submit to us an explanation of how this tragic death came about."
Over the weekend, a senior Israeli official said Australia's intelligence community was "deeply involved" in the case and had even interrogated Zygier on suspicion he was spying for the Jewish state.
Israeli daily Haaretz on Sunday reported remarks by unnamed former acquaintances of Zygier who said that he told them stories which seemed incompatible with a genuine secret agent.
The paper's defence analyst, Amir Oren, wrote that Zygier bragged to one friend, a former special forces soldier, of his Mossad connections and confided to another that during his military service he had provided backup to Israeli agents operating in Lebanon, in the course of which he had killed local children.
"Ben left the army and told me that he had been compelled to kill a boy and girl while providing security for an operation in Lebanon," Oren quoted the friend as saying.
"He told me he was hospitalised for a month with trauma. Afterward he went back to Australia and several years later returned to Israel."
"It astounds me if that could really happen," the friend added. "If so, how did they recruit him into the Mossad?"
Israel's justice ministry was on Sunday reportedly mulling whether to allow publication of the inquest into Zygier's death, which rendered a verdict of suicide.
According to Maariv newspaper, parts of it were likely to be published in the coming week after Attorney General Yehuda Weinstein decides what to delete for security reasons.
Senior legal officials are also debating whether charges of negligence should be levelled over Zygier's death.
Zygier, who immigrated to Israel in around 2001 and at some point joined Mossad, is understood to have been arrested in February 2010 on charges which remain subject to a tight gag order.
Ten months later, he was found hanged in his cell despite the fact that it was under 24-hour surveillance, sparking a welter of criticism and conspiracy theories in both Israel and Australia.