Local activists said the ISIL fighters had burned a nearby power plant and dismantled the flour mill — one of the largest in northern Syria — before withdrawing.

The London-based Syrian Observatory for Human Rights said this week that more than 3,300 people had been killed since the fighting between rival rebel groups began on Jan. 3, 2014.

Of those killed, the Observatory said 924 had been ISIL fighters, and 281 were civilians. It said 700 other fighters from both sides had been killed, but neither side had claimed them.

“The casualties have been very high because of the fighting,” said Khaled al-Milaji, the interim director at the Syrian National Coalition’s aid arm, the Assistance Coordination Unit, in Gazientep. “You can’t imagine how frustrating it is that even the guys on the front with the regime, they have to look behind them as well as at the regime in front of them, because they are sometimes hit by (ISIL) from behind.”

Safadi says that since fighting broke out with ISIL in January the number of Islamic Front fighters killed was nearly equal to half the troops killed in the previous two years fighting against Assad’s troops.

“We have more than 500 persons killed, and we have more than 1,500 injured in the past two months,” he said.

During the past two years of fighting against Syrian President Bashar al-Assad’s forces, Safadi says 1,200 troops from the Islamic Front were killed.

Even Al-Qaeda’s emissary to Syria was killed as a result of the ongoing hostilities. Two suicide bombers allegedly sent by ISIL killed Abu Khalid al Suri as he was trying to mediate an end to the fighting.

Safadi says his rehab center — one of three run by the Tawhid Association in Turkey where patients with severe injuries can rest and receive medical care between surgeries and treatments — currently has 20 patients, out of 35 total, who were wounded in the fighting with ISIL.

One of them is a 37-year-old former food importer who called himself Abu Raad.

He was shot in the hip on Feb. 3 when ISIL attacked the base he had been defending near Aleppo airport.

Abu Raad lay half covered by a blanket in a hospital bed in the six-story former office building-turned-clinic in a residential Gazientep neighborhood. His bed gave him a view out of a large, wood-framed window onto a quiet, tree-lined street below. A space heater glowed nearby as he and his four roommates watched a small TV in the corner. It showed footage of a dusty woman screaming as grimy men carried limp children down a street strewn with rubble; the aftermath of a so-called “barrel bomb” attack on one of Aleppo’s neighborhoods by Assad’s air force.

“We are fighting against two fronts — ISIL and the regime,” Abu Raad said. “We consume most of our powers fighting against ISIL. Sometimes we have to take some of our soldiers from fighting against the regime to fight against them.”

Echoing the sentiment of many opposition fighters and civilians in Syria’s north, Abu Raad claimed ISIL is funded and armed by Assad, in an effort by Damascus to weaken and divide the opposition.

“They are one of the enemies of the revolution,” he said.

Salaheddin Safadi said ISIL is on the lookout for wounded Tawhid fighters being transferred from Syria to Turkey, and had come close to capturing some of them.

On Feb. 8, he said, ISIL fighters stopped an ambulance carrying three Tawhid fighters at a checkpoint and asked for the patients’ identities.

“The ambulance driver said they were from another military group other than Tawhid in order get those guys through,” Safadi said. “(ISIL) is not good. They are speaking in a language that says ‘It’s me or nobody.’ It’s bad language.”

Being captured by ISIL could mean detention, or worse: The group has executed dozens of fighters from the Islamic Front, posting videos of the executions on YouTube.

Safidi said the infighting was only adding to the problems faced by the opposition in its fight against Assad’s government.

“No one is helping us,” he said. “We are fighting with our bare hands. It’s like playing a football game with one player against 100 players.”