BEIRUT -- The principal U.S.-backed Syrian rebel group is demanding that an Islamist insurgent faction turn over the suspected killer of one of its commanders in a slaying that has highlighted tension among allies fighting to overthrow the Syrian government.
"We demand that the perpetrators of this heinous crime be handed over to be tried by an independent judicial commission," Louay Meqdad, a spokesman for the Free Syrian Army, said Saturday in a telephone interview from Istanbul. "If they don't, then we will take measures."
The spokesman did not elaborate on the "measures," but the slaying last week of FSA commander Kamal Hamami, apparently by an Islamist rebel group, has spurred outrage in the FSA leadership.
The FSA has blamed the slaying on a powerful rebel faction, the Islamic State of Iraq and Syria, which is linked to al-Qaida. The FSA commander was shot to death on Thursday in a rebel-held stretch of northwest Syria in what appeared to be a turf dispute between the two insurgent groups, according to various accounts.
The incident has spurred fears of a "civil war within the civil war" should FSA and al-Qaida-affiliated rebel groups enter into open conflict.
But the FSA spokesman did not directly threaten retaliation, demanding only that the suspect be handed over.
How far-reaching any FSA retaliation could be remains a question. The FSA has a loose command structure and is more of a franchise operation than a top-down military command hierarchy. It is not clear how many rebel brigades identifying themselves as affiliated with the FSA actually take direction from the exiled leadership based in Turkey.
Meanwhile, U.S. officials said Saturday that Israel carried out an air attack in Syria this month that targeted advanced anti-ship cruise missiles sold to the Syria government by Russia.
The officials, who declined to be identified because they were discussing intelligence reports, said the attack occurred July 5 near Latakia, Syria's principal port city. The target was a type of missile called the Yakhont, the officials said.
Mark Regev, a spokesman for the Israeli prime minister, declined to comment on the strike, as did George Little, the Pentagon spokesman.
The Russian-made weapon has been a particular worry for the Pentagon because it expanded Syria's ability to threaten Western ships that could be used to transport supplies to the Syrian opposition, enforce a shipping embargo or support a possible no-flight zone.
The missile also represented a threat to Israel's naval forces and raised concerns that it might be provided to Hezbollah, the Lebanese militia that has joined the war on the side of the Syrian government.
The attack against the missiles came to light after Syrian rebels said that they were not responsible for large explosions at Latakia on July 5, and that a missile warehouse had been hit.
The New York Times contributed.