Istanbul, Aug 11 () - Islamic State of Iraq and the Levant (ISIL) militants have launched a new offensive against Syrian rebels north of Aleppo, gaining ground near the Turkish-Syrian border in an area where Turkey and the United States aim to create an area free of the jihadist group.

Dozens of combatants have been reported killed on both sides during fighting in and around the town of Marea, 20 kilometers south of the border with Turkey, where ISIL suicide attackers detonated four car bombs overnight, Reuters reported.
  
The attack on Marea followed the capture of a nearby rebel-held village, Umm Hosh, by ISIL fighters, the Syrian Observatory for Human Rights and a rebel commander said.
  
The rebel commander said it was the heaviest ISIL attack in the area in several months. “There is fierce fighting” he added, declining to be identified for security reasons. “The situation in northern Aleppo is bad.”

The observatory, a U.K.-based group that reports on the war using sources on the ground, said at least 25 rebels and eight ISIL fighters were killed in Marea.

Free Syrian Army attacked by ISIL

Late last month, the U.S. and Turkey announced their intention to provide air cover for rebels and jointly sweep ISIL from a strip of land near the border, a U.S. official said on July 27, confirming a Hürriyet Daily News report from July 25. 

The envisioned buffer would deny ISIL its last remaining access to the frontier with Turkey after a string of defeats by the People’s Defense Units (YPG) drove it from border positions further east.

In a statement dated Aug. 11, ISIL said its fighters had attacked two buildings in Marea and killed nearly 50 members of an “apostate” militia that opposes it.
  
The rebel commander said the targeted rebels were from a group operating under the banner of the Free Syrian Army.
  
The al-Qaeda-linked al-Nusra Front, an enemy of ISIL even though it differs little in practice and ideology, on Aug. 10 announced its withdrawal from frontline positions against the group north of the city of Aleppo. The group criticized Turkey’s plan to create a buffer, saying it served Turkey’s interests rather than the fight against President Bashar al-Assad.
  
Thought it opposes ISIL, the al-Nusra Front last month attacked rebels trained as part of a U.S.-led program to bolster insurgents viewed as moderate enough to fight the ultra-hardline group. Al-Nusra said the U.S.-trained rebels were working for U.S. interests.

Marea-Jarablus safe zone
  
ISIL, which controls wide areas of Iraq and Syria, has also launched a new attack against Syrian government forces stationed at an air base east of Aleppo in recent days.

The ISIL-free zone will be 98 kilometers long and 40 kilometers wide and situated between the Marea-Jarablus line. A good portion of this area is currently under ISIL control, and Turkey has already vowed it would not tolerate the jihadists posing a threat to the Turkish border.

Sources emphasized they have opted to call it the “ISIL-free zone” instead of a “security or safe zone” because of objections raised by Washington, who refrained from giving the wrong message to the Syrian government, as well as Russia and Iran.

The plan crafted by Ankara and Washington foresees the deployment of Free Syrian Army units to the area if ISIL is completely cleared from that particular zone, which would both prevent the Syrian Democratic Union Party (PYD) from further expanding its influence toward the West and create a putatively safe environment to shelter Syrians fleeing violence or those who want to return to their homeland.