Syria says Islamic State militants have fired shells containing mustard gas at troops in the eastern province of Deir az-Zor. The Syrian state news agency Sana reports that the poisonous gas hit military targets near Deir az-Zor air base on early Tuesday evening, affecting the breathing of a number of soldiers.

The report says the soldiers were treated immediately. It is the latest in a string of suspected mustard gas attacks by the jihadists in Syria and neighboring Iraq.