At least 16 civilians, including women and children, were killed Friday during an air raid by the Syrian regime army on the opposition-held neighborhood of Tareeq al-Bab in Aleppo, Syria's largest city, according to a pro-opposition civil defense source on the ground.

The missiles fired from a Syrian warplane also wounded 25 others, Ibrahim Abu Leys told Anadolu Agency.

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

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

The Syrian Center for Policy Research, an NGO, however, has put the death toll from the five-year conflict at as high as 470,000.