TEL AVIV — Two terrorist attacks on Israeli and Jewish targets in Buenos Aires in the 1990s that killed scores of people were carried out by a secret Hezbollah unit whose operatives, contrary to widespread claims, were not abetted knowingly by Argentine citizens or aided by Iran on the ground, according to an investigation by the Mossad, Israel’s secret service.
The internal Mossad study, the written findings of which were shared with The New York Times, provide a detailed account of how the attacks were planned — including how material for the explosives was smuggled into Argentina in shampoo bottles and chocolate boxes.
While Mossad stresses that Israeli intelligence still believes that Iran, a supporter of Hezbollah, approved and funded the attacks and supplied training and equipment, the findings counter longstanding assertions by Israel, Argentina and the United States that Tehran had an operational role on the ground. They also countered suspicions in Argentina that local officials and citizens there had been complicit.
In the first attack, which killed 29 people in 1992, the Israeli Embassy was blown up. The second, in 1994, targeted the headquarters of a Jewish community center, killing 86 people, including the bomber, in one of the deadliest anti-Semitic crimes since World War II.
The fallout from the blasts been felt for decades in Argentina, with some of those appointed to investigate the attacks later prosecuted for obstructing the investigation and top politicians accused of involvement.
The attacks also stunned Israel, which sees itself as the protector of Jews across the world, and demonstrated the global reach and growing threat of Hezbollah at the time.
The bombings were carried out by Hezbollah in revenge for Israeli operations against the Shiite militia in Lebanon, according to the Mossad investigation. It said that Hezbollah had used secret infrastructure constructed over years in Buenos Aires and other South American locations to plan attacks.
The investigation found that the explosives used in both attacks were smuggled into Argentina by Hezbollah operatives in shampoo bottles and chocolate boxes on commercial flights from several European countries. They were then stashed in a Buenos Aires park.
Chemicals used to make the bombs were acquired by a trading company used as a cover for Hezbollah’s South America operations, according to the inquiry.
The attackers were not brought to justice or killed in multiple assaults by Israel on Hezbollah over the years, and are living in Lebanon, the investigation reported.
Interpol “red notices” were issued against two people accused of being attackers, both identified in the Mossad investigation as Lebanese Hezbollah operatives. A third person is wanted by the United States. Hezbollah’s operations commander, Imad Mughniyeh, who was mentioned by the Mossad investigation as the chief of the unit that carried out the attacks, was killed in a joint Israeli and American operation in 2008.
The Mossad conclusions are based on information from agents, from the questioning of suspects, and from surveillance and wiretapping. The findings from the internal reports were confirmed in interviews this month with five current and former senior Mossad officials.
The investigation also revealed failures by Mossad, which had no advance warning of the attacks. The second was very similar to the first and was carried out by the same group, but the investigation showed that Israeli intelligence had not detected any activity preceding it.
The Mossad inquiry and the current and former officials said that Hezbollah, outgunned by the Israeli Army in Lebanon in a conventional sense, began building covert units around the world to expand its reach and attack Israelis or Jewish targets.
Starting in 1988, Hezbollah sent operatives to several South American countries to acquire “experience to enable them to open legitimate businesses and have strong commercial cover for moving around between different countries,” according to the Mossad findings.
The investigation identifies operatives by name and details forged passports and other documents used. The operatives gathered intelligence about border security, about setting up cover companies, and about possible targets, including the Israeli Embassy in Buenos Aires.
On Feb. 16, 1992, Israel assassinated Hezbollah’s leader, Sheikh Abbas Musawi.
After that attack, according to Mossad, Hezbollah sent a senior operative, Hassan Karaki, on a forged Brazilian passport to Buenos Aires, where he purchased the pickup used in the embassy attack.
The deputy commander of Hezbollah’s operations unit, Talal Hamiyah, also arrived in Buenos Aires, where he met Muhammad Nur al-Din, a 24-year-old Lebanese man who had emigrated to Brazil a few years earlier and agreed to act as a suicide bomber.
Mr. Hamiyah left Argentina a day before the attack in which Mr. al-Din blew himself up; all other Hezbollah operatives also left the country, according to the Mossad report, which also described telephone conversations between Mr. Mughniyeh, the Hezbollah commander, and his operatives.
In 2017, the U.S. Department of State offered up to $7 million for information leading to the location, arrest, or conviction of Mr. Hamiyah.
Maj. Gen. Uri Sagie, a former Israeli chief of military intelligence who recommended the assassination of Mr. Musawi, acknowledged in a 2016 interview that Israel had failed to anticipate the threat. “I did not accurately foresee Hezbollah’s reaction,” he said.
The Mossad findings said that such failures were “a very significant encouragement” for Hezbollah. In March 1994 the group also planned a suicide bombing attack in Bangkok, but the suicide bomber got cold feet and abandoned the mission.
The head of Mossad at the time, Shabtai Shavit, was warned by a senior official at the intelligence agency that there was a serious danger of another attack on Jews or Israelis in South America, especially in Argentina, according to two Israeli security officials who were serving at the time and who asked for anonymity to discuss classified topics.
Mr. Shavit believed that the operation had been carried out by Iran, not just by Hezbollah, and he ordered the monitoring of the Iranian Embassy in Buenos Aires, which showed no unusual activity, the officials said. Mr. Shavit declined to comment.
Israel continued to attack Hezbollah in Lebanon. On June 2, the Israeli Air Force attacked a Hezbollah camp, killing 50 and wounding 50 others. Hezbollah radio stations promised “a comprehensive response at all levels.”
A month later, on July 18, 1994, the Jewish community center in Buenos Aires was attacked.
According to the Mossad investigation, the same Hezbollah operatives responsible for the community center bombing were behind the downing of a Panamanian plane the next day that killed 21 passengers, including 12 leaders of the Jewish community in Panama.
The Mossad findings state that because the Hezbollah network was “not exposed and neutralized” after the attack on the Israeli Embassy, the same people could “carry out an even more deadly attack” on the community center two years later.
The bombings sent accusations flying that Argentine officials with ultraright or neo-Nazi sympathies might have been involved.
But the Mossad inquiry found no evidence for such claims.
“Only the operatives of the Hezbollah foreign operations unit took part in the attacks, without any involvement of local citizens,” it concluded.
On Iran, Mossad cited findings from an Argentine prosecutor, Alberto Nisman, that Tehran approved the two attacks, without adding details. In 2007, at Nisman’s request, Interpol issued red notices against senior Iranian officials, including Ahmad Vahidi, currently Iran’s interior minister.
Argentina, Israel and the United States have long accused Iranian Embassy officials in Buenos Aires of aiding the attacks with material and organizational help. Tehran has repeatedly denied the claims.
However, the Mossad inquiry found that Iran had not been involved in carrying out the attacks or in providing assistance. The Argentine Foreign Ministry did not immediately respond to requests for comment on the findings.
Sebastián Basso, the head of the Argentine investigation unit looking into the community center attack, on Thursday said that Iran “was the intellectual author” of the operation.
“The prosecution considers there to be enough evidence for high functionaries of the Iranian government to have to provide explanations,” he said.
Mr. Nisman was found dead in 2015 after announcing that he intended to prosecute Argentina’s president and foreign minister for making an illegal deal with Iran; the circumstances of his death remain unclear.
The attacks in Argentina reshaped the struggle between Hezbollah and Israel, making Israel more reluctant to attempt the assassination of senior members of the militant organization, according to four former Israeli officials.
That reluctance helped undermine Israel’s position against Hezbollah in the late 1990s, when it suffered heavy losses in Lebanon, eventually leading to its withdrawal from the country in May 2000, the former officials said. They added that fear of retaliation was also one of the main reasons Israel decided not to attack Iranian nuclear sites in 2012.
Ana Lankescontributed reporting from Buenos Aires.