Fighting between the Syrian arm of al-Qaeda and Western-backed rebels in northern Syria spread from Aleppo province into neighboring Idlib on Friday, the rebel group and an organization monitoring the civil war said.
Clashes began on Thursday when al-Qaeda’s Syria wing, al-Nusra Front, seized positions from the Harakat al-Hazm (Steadfast Movement) west of Aleppo, threatening one of the few remaining pockets of the non-jihadist insurgency.
A Hazm official said by telephone clashes had spread to Idlib and that his group had retaken some areas previously controlled by Nusra.
"There is now fighting in Idlib, in the Jabal al-Zawiya area," he said. In Aleppo province the two groups were also fighting in Atarib, a town 20 kilometers from the Turkish border.
The UK-based Syrian Observatory for Human Rights (SOHR) said heavy fighting overnight focused on the Regiment 46 base in western Aleppo and overlapping areas between Aleppo and Idlib province, where Nusra pushed out rebels from many areas in October.
The Observatory, which monitors the war, added Hazm had captured some small checkpoints in Idlib.
Hazm is one of the last remnants of non-jihadist opposition to President Bashar al-Assad in northern Syria, much of which has been seized by the Nusra and Islamic State of Iraq and Syria (ISIS).
Nusra said it was forced to act after Hazm detained two of its fighters and captured its weapons and offices. It said its forces had captured the Sheikh Suleiman base from Hazm, about 25 kilometers west of Aleppo, on Thursday.
"It's probably most accurate to view this as the latest instance of Nusra efforts to expand their areas of dominance in Idlib and Aleppo at the expense of Western-backed factions, which they are gradually seeking to eliminate from the north," said Noah Bonsey, senior analyst on Syria with International Crisis Group.
The Syrian Islamist militant group Ahrar al-Sham, which has worked with both groups, called for an end to the clashes and said the disagreement should be settled in an independent sharia court.
"We are ready to bring back the rights that our brothers in Nusra claimed (were taken) by Hazm," read the statement, posted on the group's Twitter account.
Both Hazm — part of the Free Syrian Army collection of mainstream rebel groups — and Nusra fight the government.
The Observatory said Nusra and other Islamist militants also fought the Syrian army in the al-Arbaeen mountain area of western Idlib on Friday. Syrian state television said the Syrian army repelled what it said were several terrorist attacks in the area. The Syrian government refers to all armed opposition groups as “terrorists.”
Hazm has received what it describes as small amounts of military aid from foreign states opposed to Assad, including US-made anti-tank missiles. But it has lost ground to better armed and financed jihadists. A Daily Beastreport revealed on Tuesday that Hazm had lost large amounts of US funding in recent months.
Meanwhile, SOHR in a separate report said that ISIS shot down a Syrian air force warplane that was bombing opposition-held areas on Thursday.
Jihadists published photographs of the plane and the pilot's body on social media sites following the crash in Damascus province. Observatory director Rami Abdel Rahman said that ISIS used anti-aircraft weapons to shoot down the plane.
