Turkey-backed Syrian National Army (SNA) forces launched a fresh offensive on the Tadef front in the area of Turkey's Operation Euphrates Shield, seizing joint Russian and Assad checkpoint in the Shaala radar base. Several pro-Russian forces were also captured alive in Tal Rahhal, local sources said Saturday.

The SNA targeted regime-held positions northeast of Aleppo, opening a new front against regime forces that have made significant advances in nearby Idlib over the last week.

The attack was focused on territory near the city of al-Bab, which has been controlled by Turkey and its Syrian opposition allies since 2017. Pro-regime media made no mention of a new attack. Turkish forces did not take part, opposition sources said.

Sources said their fighters had taken three villages so far. The Syrian Observatory for Human Rights, which monitors the war, described the fierce attack as having been "carried out by factions loyal to Ankara."

Assad regime forces, backed by Russian air support, made rapid advances in Idlib this week, capturing the town of Maarat al-Numan, located about 100 km (60 miles) southwest of al-Bab.

Idlib and the area north of Aleppo form part of the last major opposition-held territory in Syria, where Bashar al-Assad has taken back most of the ground once held by his enemies with Russian and Iranian support.

The regime's latest advance has triggered a fresh wave of civilian displacement, with hundreds of thousands moving toward the Turkish border. President Tayyip Erdoğan said on Friday Turkey may launch a military operation in Idlib unless fighting there is halted.

U.S. special envoy for Syria James Jeffrey said on Thursday the Idlib fighting raised the specter of an international crisis.

Turkey, which already hosts 3.6 million refugees from Syria, fears a fresh wave of migrants from Idlib. It has 12 military observation posts around Idlib, set up under a 2017 agreement with Russia and Iran, and several of them have since been surrounded by advancing Syrian regime forces.