In a written statement released Wednesday, the FSA said its fighters targeted "just military positions" during the Aleppo operation. "The target locations of our rocket operations are all military such as airbases, military strongholds and barracks.

"Assad regime used civilians as human shields and installed artillery and rocket launchers in vital residential areas, blatantly violating the principle of distinction in the international humanitarian law."

According to the statement, the opposition group urged civilians in regime-controlled areas to stay away from regime strongholds and their rocket launchers, and instead stay inside houses or shelters.

The statement added that FSA factions such as the Fatah Halab too were trying not to hit innocent civilians during the operation.

"Fatah Halab has avoided bloodshed by staying away from civilian areas and distinguishing fighters from civilians," the statement said.

"People of Aleppo with different affiliations and from different areas, are our people, we are fighting for them," it added.

Syria has been locked in a vicious civil war since early 2011, when Bashar al-Assad cracked down on pro-democracy protests -- which erupted as part of the Arab Spring uprisings -- with unexpected ferocity.

Since then, more than a quarter of a million people have been killed and more than 10 million displaced across the war-torn country, according to UN figures.

Anadolu Agency