Fighters from the Islamic State in Iraq and t
Fighters from the Islamic State in Iraq and tReuters

The Al-Qaeda-linked Islamist State of Iraq and the Levant (ISIS) has executed dozens of rival Islamists over the last two days, activists told Reuters on Sunday.

The executions took place as the group recaptured most territory it had lost in the northeastern Syrian province of Raqqa, according to the activists.

One of the activists, who spoke from the province on condition of anonymity, said that up to 100 fighters from the Nusra Front, another Al-Qaeda affiliate, and the Ahrar al-Sham brigade, captured by ISIS in the town of Tel Abyad on the border with Turkey, the nearby area of Qantari and the provincial capital city of Raqqa, were shot dead.

There was no independent confirmation of the report.

"About 70 bodies, most shot in the head, were collected and sent to the Raqqa National hospital," the activist told Reuters.

"Many of those executed had been wounded in the fighting. The fact that Nusra Front and Ahrar al-Sham are ideologically similar to the ISIS did not matter," he added.

In recent days, the fighting between ISIS and other Syrian rebels has escalated. Earlier Sunday it was reported that close to 500 people had been killed in the fighting between rival groups.

Three powerful rebel alliances – among them Islamist groups - have teamed up to fight ISIS, which they have warned is worse than Bashar Al-Assad’s regime.

The fact that ISIS executed rivals it caught should come as no surprise. The group has been accused of several human rights abuses, including torturing and murdering prisoners, among them children and teenagers, and forcing Druze men to convert to Islam or die.

The Al-Qaeda linked group has vowed to “crush” other rebel groups in Syria.

The group’s growth has alarmed Western nations, who are pushing the opposition to attend peace talks in Switzerland later this month, and has helped Assad to portray himself as the only secular alternative to Islamist extremism.

ISIS regrouped and recaptured much of its stronghold in Raqqa city on Sunday, activists told Reuters, dealing a blow to rival rebel groups backed by Gulf Arab and Western states.

Among those reportedly executed on the weekend was Abu Saad al-Hadram, Nusra Front's commander for Raqqa province who was captured several months, opposition sources said.