BEIRUT: Jihadists from the Islamic State of Iraq and Greater Syria (ISIS) have executed three officers of the Western and Arab-backed rebel Free Syrian Army, an activist group said Saturday.
The bullet-riddled bodies of the three were found Friday, two days after suspected Islamist militants kidnapped them in the oil-rich eastern province of Deir al-Zor, said the Syrian Observatory for Human Rights.
ISIS, which grew from the ranks of Al-Qaeda before splitting with the global terror network, is active in both Syria and neighboring Iraq and seeks to set up an Islamic state that straddles both countries.
But the radical group has faced a major backlash from other rebels fighting to topple the Syrian regime and from Al-Qaeda's affiliate in Syria, the Nusra Front, amid accusations of atrocities in Syria's three-year war.
The FSA this month called for help from "friendly and brotherly Arab nations" to fight ISIS in Deir al-Zor.
Rebels in Syria, including Nusra Front militants, have been battling ISIS since the start of the year, in fighting that has reportedly killed more than 6,000 people.
The clashes have mostly raged in the north and east of the country, and on Friday ISIS seized control of the areas of Hafez and Muhassen in Deir al-Zor.
The FSA officers executed by the jihadists had been kidnapped in Hafez, the Britain-based Observatory said.
ISIS has been battling Iraqi government forces since June 9, when in launched a lightening offensive in the north of the country.