According to sources from local field hospitals who spoke anonymously due to fears for their safety, at least nine civilians were killed in Aleppo’s Al-Sokkari district while two others were killed in the Al-Ansari district.

Meanwhile, Najib al-Ansari, a civil defense official based in Aleppo, told Anadolu Agency that Russian and regime warplanes had carried out 150 separate airstrikes in Aleppo late Wednesday.

"Russian aircraft attacked [Aleppo’s] Bustan al-Qasr neighborhood with phosphorus bombs, leaving several residential buildings in flames," al-Ansari said.

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

The Syrian Center for Policy Research, a Beirut-based NGO, has put the death toll from the six-year-old conflict at more than 470,000.