As the Turkish military offensive against Syrian Kurdish forces enters its fourth day, Syrian Arab rebels whose main purpose remains to topple President Bashar al-Assad's regime are at the front lines on Turkey’s side.

The Free Syrian Army (FSA), a loose coalition of mainly Sunni Arab rebel forces, captured a strategic village and two hills in Afrin, the mainly Kurdish region that is the focus of the Turkish campaign, Turkey’s state run Anadolu news agency reported today. Clashes between the Kurdish fighters known as the People’s Protection Units (YPG) and the Turkish-led forces continued to rage near the Qastal Jendo hill on the northern border of Afrin, with the YPG claiming it had swiftly recaptured lost ground.

Turkish airstrikes and shelling have left at least 24 civilians — including six children — dead since the start of the Turkish offensive called “Olive Branch,” the London-based Syrian Observatory for Human Rights (SOHR) said in an update.

Cut off on all sides by Turkey and its allies and regime forces, Afrin is facing a humanitarian crisis. US Secretary of Defense Jim Mattis warned that the Turkish operation “risks exacerbating the humanitarian crisis that most of Syria is going through.” Mattis added, "In the Afrin area we had actually gotten to the point where humanitarian aid was flowing, refugees were flowing back in … the Turkish incursion disrupts that effort.”