Seven people were killed and another 32 injured on Friday by barrel bombs dropped by Syrian regime aircraft in the northwestern Aleppo province, local civil defense sources told Anadolu Agency.

The sources, who spoke anonymously due to security concerns, said regime helicopters had dropped barrel bombs on Aleppo's opposition-held towns of Anadan and Khan al-Asal.

Women and children were among the casualties, they said.

The injured, meanwhile, were taken to field hospitals set up in both towns.

Barrel bombs are improvised containers packed with shrapnel and explosive material.

Usually dropped from army helicopters, these low-cost munitions are believed to have killed thousands of people in Syria since the conflict began more than five years ago.

Syria has been locked in a vicious civil war since early 2011, when the Assad regime cracked down on pro-democracy protests with unexpected -- and disproportionate -- ferocity.