ALEPPO, Syria 

At least 46 civilians were killed in regime attacks in the northwestern city of Aleppo, local sources told Anadolu Agency late Thursday.

Necip Ensari, a civil defense official operating in the city, said 230 others were injured in the attacks.

Ensari said “bombs containing chlorine gas” were used by Syrian army military helicopters to attack opposition-controlled areas.

“A large number of people were affected by the gas that spread around at the attack,” he added.

A total of 935 civilians have been killed in regime attacks in the area since mid-November, according to figures released by local civil defense officials.

The bombardments have forced hospitals and other medical facilities in the battered city to cease operations while most academic activities have been completely halted.

The stepped-up attacks come within the context of attempts by the Russia-backed Bashar al-Assad regime and its allies to wrest control of eastern parts of the city four years after they were captured by armed opposition groups.

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

Since then, hundreds of thousands of people have been killed and millions more displaced by the conflict.