According to sources at local field hospitals who spoke anonymously due to fears for their safety, warplanes targeted residential neighborhoods in the city’s Al-Ansari, Al-Sokkari, Tariq al-Bab and Al-Shear districts -- all of which remain under siege by regime forces.

Ibrahim Abu Laith, an Aleppo-based civil defense official said that Russian jets had struck civil defense centers and fire departments in the city’s Al-Ansari and Masaken Hanano districts.

A number of ambulances, he added, had been destroyed by the airstrikes.

Syria has been locked in a devastating civil war since 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.