The United States military has killed 100 Syrian soldiers loyal to President Bashar al-Assad in airstrikes in the province of Deir ez-Zor after the troops allegedly started a coordinated assault on Syrian opposition forces, AP reported on Thursday. The strikes were carried out in self-defence after the pro-Assad troops started firing artillery and tank rounds at the US-backed Syrian Democratic Forces, the US military claimed.

“After 20 to 30 artillery and tank rounds landed within 500 metres of the SDF headquarters location, Syrian Democratic Forces supported by the coalition targeted the aggressors with a combination of air and artillery strikes,” Colonel Thomas Veale of the Combined Joint Task Force Operation Inherent Resolve, that is assisting in the battle against the Islamic State in Iraq and Syria, said. “Coalition advisers were with the SDF in an advise, assist and accompany capacity, and this action was taken in self-defense.”

Asked why the pro-Assad troops had launched the attack, Colonel Veale said they were likely trying to capture oilfields in the region that had been liberated from the Islamic State in September 2017, Politico reported. The coalition spokesperson said that before and after the battle it made efforts to avoid confrontation with Russian forces in the area that are supporting the Assad regime.