JERUSALEM -- 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.
Mr. 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 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 he was seeking "an explanation" from Israel for a report that his ministry is preparing about the case.
Mr. 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," Mr. 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," he 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 tranquility in the state of Israel."
It was unclear what effect Mr. 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 cover-up 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.
News reports in Australia said Zygier had been under investigation there on suspicion of working for the Mossad, and that Australian security officials suspected that before his arrest he may have been about to disclose information to the Australian government or the media about the use of fake passports by the Israeli spy agency.