Syria's state media is accusing rebel forces of using a chemical weapon.
"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," the official SANA news agency, controlled by President Bashar Assad's regime, reported on Tuesday.
Aleppo, a little more than 190 miles northwest of Damascus, is Syria's largest city. In one of the worst mass executions in Syria's civil war, at least 79 bodies were discovered floating in one of Aleppo's rivers at the end of January.
The Syrian government is believed to have one of the world's largest arsenals of chemical and biological weapons.
At a security conference in Herzliya last week, Israeli Military Intelligence chief Maj.-Gen. Aviv Kochavi warned that Assad is preparing to use chemical weapons.
Israel has long been concerned that the chemical weapons cache could wind up in the hands of al Qaeda-affiliated Islamist rebels fighting the regime, as well as the Lebanese-based Hezbollah terrorist group.