The Australian ABC reported that the prisoner, who it referred to as Ben Zygier, migrated from Australia to Israel in 2000 and had worked for Mossad. It reported that his incarceration was top secret, but did not say why he had been arrested.

According to the report, the affair was first exposed in June 2010, when the Israeli news site Ynet briefly reported on the existence of a prisoner — identified only as Prisoner X — whose crimes were unknown. The report was removed from the site shortly after it was posted, apparently by the censor.

Ynet then reported on Dec. 27, 2010, that a prisoner had committed suicide while in solitary confinement two weeks earlier. That report, which said jailers took him down from his noose and unsuccessfully tried to revive him, was also quickly removed.

ABC strongly suggested that prisoner was Ben Zygier.

After the ABC report aired and was posted online, at least two Israeli news sites published — and then swiftly removed — articles citing the report.

The Haaretz daily then reported about the emergency meeting called by Israeli Prime Minister Benjamin Netanyahu, where he urged the editors of the major news outlets to refrain from publishing details about the ‘‘embarrassing’’ matter.

Almost instantly, foreign press began publishing stories about the affair online. Bloggers were deliberating the circumstances of the man’s death and a flurry of speculation filled Twitter feeds. Some Twitter users, including Israelis, circulated what they claimed were photos of Zygier and his family’s phone number.

Late Wednesday, after a day’s uproar over the issue, Israel finally confirmed that an Australian prisoner had been held under a false name and that his family knew.

Israeli authorities have also sought to suppress knowledge of the detention of Arab engineer Dirar Abu Sisi, who vanished after boarding a train in Ukraine on Feb. 19, 2011, only to resurface in Israel three weeks later in detention.

In that case, an Israeli court issued a gag order on his detention. But reports quickly surfaced out of Ukraine and the Gaza Strip about his disappearance and incarceration in Israel.

Abu Sisi was ultimately accused of masterminding Hamas’ rocket program and training fighters in the Gaza Strip and was charged with a number of crimes.

In 2010, a court-ordered ban prevented local reporting of the case of Anat Kamm, a former female soldier charged with leaking more than 2,000 military documents to a newspaper. The case was reported extensively in blogs and foreign press, which Israeli media were initially forced to cite before the gag order was lifted.

Miri Regev, a lawmaker and former chief censor, conceded to Army Radio that the censorship may be ‘‘draconian’’ but said Israel has legitimate security reasons to continue it. She said Israel’s decision to ban reporting on the ABC report was a step too far.

‘‘We could have avoided these 16 hours (of silence). We could have published the information that was published today,’’ she said. ‘‘We would have avoided the discussion surrounding this.’’

Nonetheless, she wrote on her Facebook page that the attorney general should investigate the lawmakers who broke the gag order and urged an investigation into who leaked information about the prisoner to the media.

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