Supporters of Hezbollah carry the coffin of Jihad Imad Mughniyeh, son of late Hezbollah leader Imad Mughniyeh, in Beirut. (Nabil Mounzer/European Pressphoto Agency)

Lebanon and Israel braced Monday for possible retaliation by Hezbollah for the deaths of six of the group’s fighters in an alleged Israeli raid in Syria, as Iran confirmed that one of its senior military commanders was also killed in the attack.

The strike on Sunday, in which Israeli helicopters fired missiles at Hezbollah vehicles traveling in a Syrian-controlled portion of the Golan Heights, sent regional tensions soaring at a critical time, prompting fears of another war such as the one that erupted in 2006 with sudden and unexpected ferocity.

What form such retaliation might take — or whether there would be any at all — was the subject of intense speculation as the potential for spillover from Syria’s war took yet another unpredictable twist.

“It’s in the common interest between Hezbollah and Iran to retaliate,” said Eyal Ben-Reuven, a retired Israeli major general who commanded troops during the 2006 war. “We should prepare ourselves for every kind of scenario.”

That one of those killed in the strike was the son of Imad Mughniyah, a revered Hezbollah military commander assassinated in a 2008 bombing also widely blamed on Israel, compounded expectations that Hezbollah would feel compelled to respond.

Iranians carry a placard bearing the picture of Mughniyeh and his father. (Atta Kenare/AFP/Getty Images)

Chanting “Death to Israel,” thousands of angry Hezbollah supporters thronged the funeral of Jihad Mughniyah as his coffin was escorted to Hezbollah’s Martyrs’ Cemetery in Beirut’s southern suburbs, where he was buried alongside his father.

Although the younger Mughniyah, 25, was nowhere near as senior as his father, or even some of the other commanders killed in the attack, the family name resonates deeply, and there were widespread calls for revenge. A hashtag, #je_suis_jihad_imad_moghnia, rapidly circulated among Hezbollah supporters on Twitter.

“People are angry and want a quick retaliation,” said a Hezbollah member who attended the funeral and spoke on the condition of anonymity because he is not authorized to speak to the media.

Israel is believed to have conducted at least five previous airstrikes in Syria over the past two years, mostly targeting suspected shipments of sophisticated Iranian weaponry from Syria to Hezbollah in Lebanon. Both Iran and its ally Hezbollah have played a vital role in sustaining Syrian President Bashar al-Assad’s hold on power against the mostly Sunni rebellion seeking to unseat him, by sending men, money and arms to support his depleted army.

Hezbollah and Iranian commanders reportedly also died in those attacks, but this was the first to kill such senior figures, and also the first to have elicited such a public response from Hezbollah. Israel has neither confirmed nor denied any of the strikes, including this one, which Israeli officials quoted by news agencies have said was intended to preempt a planned Hezbollah infiltration into Israel.

Iran called the attack “a terrorist act” but did not indicate whether it intended to retaliate for the death of one of its top commanders in Syria. The commander was identified as Brig. Gen. Mohammed Aliallah Dadi of Iran’s Revolutionary Guard Corps, who was serving as a “military adviser to the Syrian government,” according to the official Iranian news agency IRNA.

Some Lebanese and Israeli media reports identified Dadi as Iran’s most senior commander in Syria. One of the Hezbollah commanders killed, Mohammed Issa, was also said to be the Shiite Lebanese movement’s top leader in Syria, raising questions as to why such a prominent group of leaders was traveling so close to Israel’s border in such a sensitive area. Israeli officials cited by news agencies said Israel was seeking to preempt an attack planned by those who were killed, while some analysts suggested Israel had simply taken advantage of the opportunity to kill a top cadre of officers.

Intensifying expectations that Hezbollah will respond to this attack came three days after Hezbollah’s leader, Hasan Nasrallah, made unexpectedly belligerent comments against Israel in a television interview, warning for the first time that Hezbollah would react if Israel carried out further strikes in Syria.

“No one has given a commitment that the attacks against Syria will remain without a response,” he said. “This is the right of the axis of resistance, and it is not Syria's right exclusively.

“When will this right be practiced? This depends on certain criteria that will be taken into consideration,” he added.

Yet at a time when Hezbollah’s resources are stretched by its entanglement in Syria, such a response seems unlikely, said Hilal Khashan, a professor of political science at the American University of Beirut.

“It seems that Israel called Nasrallah’s bluff,” he said. Even if Hezbollah were not preoccupied with Syria, its role in Lebanon, where it is striving to maintain a delicate balance of power with rival Sunni and Christian factions adamantly opposed to embarking on another devastating war would preclude the risk of provoking Israel.

“It will not retaliate,” he predicted. “Hezbollah does not want to go to war with Israel.”

The attack coincides with a crucial juncture in Iran’s negotiations with the United States over ways to curb Iran’s nuclear program in return for sanctions relief, which gives Iran little incentive to escalate tensions with Israel, America’s closest ally, Khashan and other analysts said.

Those sympathetic to Hezbollah, however, said that a response of some kind was inevitable, either in the form of terrorist attacks against Israeli targets elsewhere in the world or a direct attack on Israel.

Any such response would probably draw Iran and Syria into the equation, said Salem Zahran, a Lebanese analyst and journalist with close ties to Hezbollah and the Syrian government. “It will be an Iranian-Syrian-Hezbollah retaliation,” he said.

In an interview with Israel’s Army Radio, Maj. Gen. Amos Yadlin, the former head of Israel's Military Intelligence, said Hezbollah faced intense pressure to respond.

“Hezbollah and Nasrallah will have to consult with their Iranian masters and take into consideration whether a fierce response will drag the region into war,” Yadlin said.

Booth reported from Jerusalem. Suzan Haidamous and Hugh Naylor in Beirut also contributed reporting.