Syria’s state news agency accused rebels on Tuesday of using chemical weapons in an attack in the northern province of Aleppo which it said killed 15 people.

“Terrorists fired a rocket containing chemical substances in the Khan al-Assal area of rural Aleppo and initial reports indicate that around 15 people were killed, most of them civilians,” SANA news agency said.

It was not immediately possible to verify the report and SANA gave no further details. There was no immediate response from Syrian rebel forces.