A Hezbollah statement said an Israeli helicopter fired missiles on Sunday at Jihad Mughniyeh's car in Quneitra, near the Israeli-occupied Golan Heights, killing a total of six members of the group.
Mughniyeh, 20, was the son of Imad Mughniyeh, who was killed in the Syrian capital Damascus in 2008, also in a suspected Israeli attack.
Imad Mughniyeh was on the most-wanted list of the US for attacks on Israeli and Western targets until his killing.
"Mohamad Issa, the chief of Hezbollah operations in Syria, who died in the air strike, is also a big name, making this a major strike on Hezbollah," Al Jazeera's Nicole Johnston, reporting from Beirut, said.
"The group says there will be retaliation for the attack."
Iran's semi-official Tabnak news site reported that the air assault also killed several Iranian troops, who along with Hezbollah – a Lebanese political group with a powerful military wing and close ally of Tehran – are backing Syrian forces loyal to Syrian President Bashar al-Assad against rebels.
State-run Iranian television said that the identity of the "martyrs" could not be confirmed.
The Hezbollah-run al-Manar news channel said that the Israeli attack suggest "the enemy has gone crazy because of Hezbollah's growing capabilities and it could lead to a costly adventure that will put the Middle East at stake".
Israeli Channel 10 television quoted an official Israeli source as confirming the country's role in the attack.
Israel's Ynet news website also quoted a military source as saying that the operation targeted "terrorists who intended to attack Israel".
"This is the seventh time Israel has attacked targets close to its borders since the war in Syria started," Al Jazeera's Nisreen El-Shamayleh, reporting from the Jordanian capital Amman, said.
A statement on al-Manar television said the fighters were killed during a field reconnaissance mission in Mazraat Amal, a village in Quneitra.
The incident happened three days after Hassan Nasrallah, the Hezbollah leader, said he considered frequent Israeli attacks in Syria as a major aggression, and that Syria and its allies had the right to respond.
Nabil Boumonsef, a columnist at the Lebanon newspaper an-Nahar, said he believed the strike was a direct response to Nasrallah's speech and could lead to a backlash.
"Killing the son of Mughniyeh is dangerous. I do not think that the group can be quiet now, now that the father and the son are killed. I expect that it will do something," he said.
Source:ereporter