Israeli Prime Minister Benjamin Netanyahu, left, heads the weekly cabinet meeting in Jerusalem, Sunday, Feb. 17, 2013. Netanyahu is defending the actions of Israel's security forces following a public uproar over the mysterious death of a man who apparently hanged himself while being held secretly in a maximum-security prison. (Ronen Zvulun/AP)

Wading into the furor surrounding the death in secret custody of an Australian-Israeli man reported to have been an Israeli spy, Prime Minister Benjamin Netanyahu said Sunday that “overexposure” of intelligence activities could seriously harm national security, and that Israel’s security agencies should be allowed to get on “quietly” with their jobs.

Netanyahu made his first public remarks on the case after days of intense media coverage and calls for an investigation into the mysterious death of the man initially known as “Prisoner X” and later identified in media reports as Ben Zygier, 34, an immigrant from Australia who became an agent of the Israeli spy agency Mossad.

Jailed secretly under a sweeping gag order imposed by an Israeli court, Zygier died Dec. 15, 2010, after nearly 10 months in solitary confinement in a maximum-security cell. Israeli authorities have ruled the death a suicide.

The court order prevented publication of information about the case for more than two years until a report last week by the Australian Broadcasting Corp., which said Zygier had hanged himself, led Israeli authorities to acknowledge the prisoner’s death after initially trying to prevent local media outlets from publishing the story.

The authorities did not identify Zygier or provide information on what crimes he was accused of, why he was held in isolation and how he managed to kill himself in a cell that was supposed to be under round-the-clock surveillance. Some members of Israel’s parliament have called for an inquiry, and Australian Foreign Minister Bob Carr said Sunday that he was seeking “an explanation” from Israel for a report that his ministry is preparing about the case.

Netanyahu tried to parry ac­cusations that Israel’s security agencies, acting under a cloak of secrecy that critics say prevented public oversight, had gone too far in the name of national security.

“The security and intelligence forces of Israel act under the full supervision of the legal authorities, which are completely independent,” Netanyahu said in remarks at the start of the weekly meeting of his cabinet.

“In this combination of maintaining security and abiding by the law, freedom of speech is also maintained, but overexposure of security and intelligence activity can damage, sometimes even seriously damage, national security,” Netanyahu said.

“We are not like other countries,” he added. “We are more threatened, more challenged, and therefore we must maintain proper activity of our security agencies, so I ask everyone — let the security forces carry on their work quietly so we can continue living in security and tranquillity in the state of Israel.”

It was unclear what effect Netanyahu’s remarks would have on the uproar provoked by the case, which has raised questions in Israel about the balance between national security and the public’s right to know, and about whether the authorities were involved in a coverup of possible failures or misdeeds that led to the prisoner’s death.

More details are expected to be released this week on the findings of an Israeli coroner’s inquest into the circumstances of Zygier’s demise, but nothing has been said by Israeli officials about the nature of the charges he faced, which remain concealed by the gag order.

A report Monday by the Australian Broadcasting Corp. said that Zygier was arrested after he gave Australian intelligence agents detailed information about Mossad activities, including a planned top-secret operation in Italy. Earlier Australian news reports said Zygier had been under investigation by Australia’s intelligence agency on suspicion of using his Australian passport to work for the Mossad.

A report last week in al-Jarida, a Kuwaiti newspaper, linked Zygier to the January 2010 assassination of a senior Hamas operative in Dubai, Mahmoud al-Mabhouh. Citing “senior Western sources,” the paper said Zygier had been part of the hit team and provided Dubai authorities with detailed information, including names and pictures, in return for protection, but he was seized and brought back to Israel.

Zygier’s arrest, which Carr said was reported by the Israelis to Australian intelligence in February 2010, coincided with revelations by Dubai police that the suspected Mossad assassins had used fake European and Australian passports.

With the charges against Zy­gier undisclosed, criticism in Israel has focused on the management of the affair by the authorities.

Tzachi Hanegbi, the head of parliament’s Foreign Affairs and Defense Committee at the time of Zygier’s detention, told Israel Radio on Sunday that although his committee received frequent intelligence briefings on issues of national security, it was not told about the prisoner.

“This requires an explanation,” said Hanegbi, a member of Netanyahu’s Likud party.

A subcommittee on intelligence said Sunday that it would carry out an “intensive examination” of the case.

Michael Sfard, a prominent human rights lawyer, said the greatest flaw in the handling of the case was the conduct of secret legal proceedings against Zygier. “A secret trial should go against the basic instincts of every judge,” he said. “A trial without the presence of the public is like a trial without the defendant. . . . It’s a recipe for a miscarriage of justice.”

Dan Yakir, chief legal counsel for the Association for Civil Rights in Israel, which had unsuccessfully challenged the gag order, said it was symptomatic of the stepped-up use of such orders in recent years to suppress information whose publication would not have been banned by the military censor because it posed no imminent security threat.

The sweeping prohibition of any mention of Zygier’s imprisonment and death was “exaggerated,” Yakir said. “Covering up shortcomings only weakens the Mossad, because the lack of public oversight enables such bodies to avoid investigation and correction of what went wrong.”