BEIRUT — An Israeli strike in southern Syria on Sunday killed the son of a slain top Hezbollah commander and four other fighters from the Lebanese Shiite militant group, which has been fighting alongside Syrian government forces, an official said.

The strike targeted two Hezbollah vehicles as fighters were inspecting positions in the Golan Heights, close to the Israeli-controlled frontier, in an area known as Mazare al-Amal.

A Hezbollah official identified one of the five slain men as Jihad Mughniyeh, the son of Emad Mughniyeh, a top Hezbollah operative assassinated in 2008 in Damascus. Hezbollah blames Israel for the killing and has long vowed to avenge his death.

The official spoke on condition of anonymity because he was not authorized to brief the media.

Hezbollah’s media wing said “a number” of fighters were killed, but did not provide names.

“While a group of Hezbollah fighters were on a field inspection of the town, Mazare al-Amal… They faced rocket shelling from helicopters of the Israeli enemy, leading to the martyrdom of a number of holy warrior brothers, whose names will be announced once their honorable families have been informed,” it said.

A spokesman for the group, Mohammed Afif, said the men were in two vehicles when they were hit.

The Britain-based Syrian Observatory for Human Rights, which relies on activists inside Syria, said Israeli airstrikes targeted two vehicles in the area.

Syria’s state-run media said six people were killed, and that a child was seriously wounded.

Israel’s military did not comment on the report.

A Syrian activist said Hezbollah was widely rumored to be training pro-Assad militiamen and Syrian government forces near the area. The activist, who uses the name Abu Omar, said the tiny community was close to rebel positions, and that they had obtained the information from people there.

Hezbollah fighters have been battling alongside forces loyal to Assad against rebels seeking his ouster. Israel has retaliated against the militant group in the past, and Israel and Hezbollah fought a devastating war in the summer of 2006.