On Wednesday, two jihadists -- one on a motorcycle and the other in a car -- detonated themselves in the Bir Hassan district of Beirut, a Hezbollah enclave, killing six other people and wounding dozens of others near the Iranian Cultural Center.
It was the sixth suicide bombing in Lebanon attributed to jihadist groups in less than four months, an unprecedented assault on Hezbollah.
The attacks demonstrate how Hezbollah is having to contend with being hoisted on its own petard, and its inability to protect its civilian areas from groups such as the Abdullah Azzam Brigades, which claimed responsibility for Wednesday's bombings.
Other bombings have been carried out by the jihadist al-Nusra Front and the Islamic State of Iraq and the Levant, Iraq-based groups fighting in Syria's bloody civil war against Hezbollah, whose fighters are aiding the embattled regime of President Bashar Assad.
The Brigades say they will go on bombing until Hezbollah withdraws from Syria, something Hezbollah leader Hassan Nasrallah says he will never do as long as the Assad regime, Iran's key Arab ally, is under threat.
The Brigades, named after Osama bin Laden's Palestinian mentor during the 1979-89 war in Afghanistan, also claimed the Nov. 19 double suicide bombings of the Iranian Embassy in Hezbollah's stronghold in south Beirut known as the Dahiyeh. The blasts killed 23 people.
For Hezbollah, having the embassy of its patron, Iran, blown up was an immense blow to the organization's prestige and its aura of invincibility.
But the jihadists have still not been able to deliver a crippling blow to Hezbollah, although its combat losses in Syria are mounting, with 300 killed and 1,000 wounded, according to Israeli estimates.
"The Sunni groups' attacks are frequently flawed operationally," said the U.S. global security consultancy Stratfor.
Even so, the suicide bombings, hitting at the heart of Hezbollah's civilian support, along with the losses in Syria, are starting to dismay the group's loyalists and raise questions about Hezbollah fighting Arabs to support for a brutal dictator rather than fighting the traditional enemy, Israel.
"Hezbollah's desire to work with moderate Sunni leaders to reach a truce with Sunni jihadists was one of the driving factors for its efforts to help" form a new government announced Sunday, Stratfor observed.
Hezbollah's highly efficient security service, aided by Lebanon's military intelligence, has tracked down several jihadists linked to the bombings and intercepted car bombs that were to be driven into Hezbollah enclaves in Beirut and the Bekaa Valley in northeast Lebanon, Hezbollah's heartland.
Sheik Omar al-Atrash, a Sunni cleric charged with masterminding the terror attacks, was arrested Jan. 22. He apparently betrayed other jihadists.
Meantime, the bombings go on, seen by many as payback for Hezbollah's history of pioneering suicide operations, even though these were rarely directed against other Lebanese.
The first suicide bombing is generally attributed to an Iranian-backed Iraqi Shiite group, Al-Dawa al-Islamiyya, or the Islamic Call, in Beirut on Dec. 15, 1981, in the early days of the eight-year Iran-Iraq war.
A member of the group, which played a key role in Iran's creation of Hezbollah in Lebanon in 1982, drove a white Mercedes packed with 220 pounds of high explosives into the Iraqi Embassy in Beirut.
The blast killed 61 people, including Ambassador Abdul Razak Lafta, and ushered in the era of the suicide strategy Hezbollah adopted.
It carried out its first suicide attack in Tyre, south Lebanon, against a security headquarters of the invading Israeli military. It killed 76 Israeli soldiers.
Over the next 16 years, Hezbollah carried out 37 suicide bombings, by the count of Israel's Institute for National Security Studies think tank.
Among the deadliest was the April 18, 1983, bombing of the U.S. Embassy in Beirut that killed 63 people, 17 of them Americans.
On Oct. 23 that year, a suicide bomber rammed a truck carrying 2,000 pounds of explosives into the U.S. Marine barracks at Beirut's airport, killing 241 servicemen. A simultaneous attack on a nearby French base killed 58.
Then came Sept. 11, 2001, when al-Qaida took suicide bombing to an unprecedented level of ferocity.