Israel's parliament announced plans on Sunday for an intensive inquiry into the 2010 arrest and death of a jailed Australian-Israeli citizen believed to have worked for or with the Mossad secret service.

"The intelligence subcommittee of the foreign affairs and defense committee decided to hold an intensive inquiry into all aspects of the affair of the prisoner found dead in his cell," the panel's spokesman said without providing further details.

Ben Zygier, generally known as "Prisoner X," died in December 2010, with his story first coming to light in a report by the Australian Broadcasting Corporation on Tuesday.

The Israeli media was briefly gagged on the matter, even after it became world news, according to the left-leaning Haaretz newspaper, but Prime Mininster Benjamin Netanyahu ultimately permitted reports on Zygier.

The 34-year-old was found hanged in his cell at a high-security prison. He is said to have committed suicide.

Netanyahu requests quiet

In his first public comments on the matter, Netanyahu appealed for continued discretion in the case, citing security concerns.

"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," Netanyahu told the Cabinet in remarks communicated by his office. "In the reality in which Israel lives, it must be a central interest."

Netanyahu also expressed his "complete trust" in the country's security forces.

Israel has a largely free press, though all journalists must agree to abide by censorship requests from the military or on other security grounds in order to receive accreditation. Reporters Without Borders ranked Israel 112th out of 179 countries in the 2013 edition of its World Press Freedom Index.

Australian Foreign Minister Bob Carr has announced that his office was preparing a report on the fate of Zygier, saying the government in Canberra had asked Israel to contribute.

"We want to give them an opportunity to submit to us an explanation of how this tragic death came about," Carr said.

There is still little concrete information concerning what role, if any, Zygier had within the Mossad secret service or the conditions of his imprisonment - believed to have run from February 2010 until his death on December 15.

msh/jm (AFP, dpa, Reuters)