Rebels led by Islamist militant group Hayat Tahrir al-Sham launched an incursion on Wednesday into a dozen towns and villages in the northwestern province of Aleppo, which is controlled by Syrian President Bashar al-Assad's forces.
The attack was the biggest since March 2020 when Russia, which backs Assad, and Turkey, which supports the rebels, agreed to a ceasefire that ended years of fighting that uprooted millions of Syrians opposed to Assad's rule.
Smoke rises amid fighting between factions and Syrian government troops in Dadikh, Syria. (AP PHOTO)
In its first statement since the surprise campaign, the Syrian army said it had inflicted heavy losses on what it described as terrorists who had attacked on a wide front.
The army on Thursday said it was co-operating with Russia and unnamed "friendly forces" to regain ground and restore the situation.
Rebels advanced almost 10km from the outskirts of Aleppo city and a few kilometres away from Nubl and Zahra, two Shi'ite towns where Lebanon's Iran-backed Hezbollah has a strong militia presence, an army source said.
They attacked al-Nayrab airport east of Aleppo, where pro-Iranian militias have outposts.
Russian jets pounded newly captured areas and hit populated towns in the last opposition-held enclave, according to two army sources.
Internally displaced Syrians have been sheltering in the town of Al-Bardaqli, north of Idlib, Syria. (EPA PHOTO)
Rebels say the campaign responded to stepped-up strikes in recent weeks against civilians by the Russian and Syrian air forces on areas in southern Idlib province, in Syria's far northwest, and to pre-empt any attacks by the Syrian army, which they said was building up troops near front lines with rebels.
Meanwhile Iranian state media said Revolutionary Guards Brigadier General Kioumars Pourhashemi, a senior Iranian military adviser in Syria, was killed in Aleppo by rebels.
Iran has sent thousands of fighters to Syria during the Syrian war. While these have included members of the Guards, officially serving as advisers, the bulk have been Shi'ite Muslim militiamen from all over the region.
Pro-Iranian militias have an extensive military presence in the Aleppo countryside.
There were 85 air strikes from Russian and Syrian war planes in the past 36 hours. (EPA PHOTO)
Turkish security sources on Thursday said the rebels initially launched a limited operation after attacks by Syrian government forces, and expanded the operation after government forces abandoned their positions.
The Turkish sources said the rebel movements remained within the boundaries of a de-escalation zone in Idlib, which was agreed in 2019 by Russia, Iran and Turkey with the aim of reducing hostilities between the rebels and government forces.
A Turkish defence ministry source said Turkey was following developments in northern Syria closely, and had taken precautions to ensure the security of Turkish troops there.
Hayat Tahrir al-Sham, listed as a terrorist organisation by the United States and Turkey, has long been targeted by Syrian government and Russian forces.
It competes with more mainstream rebel groups backed by Turkey that also control swathes of territory along the Turkish border.
The rebels say more than 80 people, mostly civilians, have been killed in 2024 in drone strikes on rebel-held villages.
Damascus says it is waging a war against al Qaeda-inspired militants and denies targeting civilians indiscriminately.Â
