Jihad Mughniyah, seen in this Feb. 22, 2008 photo, was one of six Hezbollah fighters killed Sunday in Syria, the group said. (Hussein Malla/AP)

An Israeli air raid over Syria killed six members of Hezbollah on Sunday, the Lebanese Shiite group announced, adding to a recent escalation in tensions between the longtime foes, who fought a devastating war in 2006.

Hezbollah said in a statement that Israeli helicopter fire had killed several of its fighters in the Quneitra region of southern Syria, an area bordering the Israeli-held Golan Heights. The group’s al-Manar TV broadcast a warning that Israel was “playing with fire,” and some observers worried that the incident could ignite what has become an increasingly combustible situation.

“We are at the edge of a war with Israel that will take place on Syrian territory,” said Salem Zahran, a Lebanese political analyst who is close to Hezbollah and the government of Syrian President Bashar al-Assad.

Hezbollah said in a statement that at least six fighters were killed in the raid, including Jihad Mughniyah, the son of Imad Mughniyah, a former top militant in the group who was assassinated in a 2008 car bombing in Damascus, the Syrian capital. Israel is suspected of playing a role in the elder Mughniyah’s killing.

Lebanon’s Daily Star, citing unnamed sources, reported that as many as 10 were killed in the attack.

Hezbollah militants are fighting in Syria against the opponents of the Assad government, although they are not thought to have mounted attacks against Israel from Syrian territory.

A spokesman for Hezbollah, Mohammed Afif, said the men were in two vehicles at the time of Sunday’s raid, the Associated Press reported.

Israel’s military did not comment on the incident.

The attack follows particularly tough comments against Israel made by Hezbollah’s leader, Hasan Nasrallah, during an interview broadcast by Lebanese television Thursday. In it, he warned of retaliation against further Israeli attacks in Syria, saying that the group could invade northern Israel and has “sophisticated missiles” that are ready for use.

Sunday’s raid brings to five the number of Israeli airstrikes in Syria since 2013, some of which are thought to have targeted arms destined for Hezbollah. Analysts have said the strikes are meant to deter shipments of Iranian weapons to Hezbollah, which relies on the Assad government to facilitate the flow of arms from Tehran, the group’s foremost ally. Hezbollah’s military objectives in the Syrian civil war include keeping those weapons-supply lines open.

Israeli military officials have expressed concern recently about Hezbollah’s weapons as well as its military activities, which include stepped-up surveillance of Israeli military movements along the Israel-Lebanon border. According to some estimates, Hezbollah possesses more than 150,000 rockets — far more than it is thought to have had in 2006. During the war that year, the group, which is classified as a terrorist organization by the United States, rained down scores of rockets on Israeli cities.

Brig. Gen. Itai Brun, head of the Israeli military’s intelligence division, told the Israel Hayom newspaper last week that Hezbollah also has plans to mount incursions inside Israel during future conflicts. “Unlike in the Second Lebanon War, I believe that next time we will see Hezbollah forces on Israeli soil,” Brun was quoted as saying, referring to the Israeli name for the 2006 conflict, which lasted 34 days and left more than 1,100 Lebanese and 165 Israelis dead.

Israeli officials have watched with growing concern recent developments in the Golan Heights. The Israeli-held side of the strategic plateau has been hit regularly by mortar fire during the Syrian civil war. Meanwhile, on the other side of the Golan, al-Qaeda’s arm in Syria, Jabhat al-Nusra, has seized large chunks of territory from Assad’s forces.

Jonathan Spyer, director of the Rubin Center, a think tank at Israel’s Interdisciplinary Center Herzliya, said the Hezbollah fighters killed Sunday could have been targeted for attempting “to try and change the rules of the game by planning attacks against Israel from inside Syria.”

He called the Israeli strike “a major event,” adding that a Hezbollah response “is quite likely.”

Suzan Haidamous in Beirut and Ruth Eglash in Jerusalem contributed to this report.