Story highlights Bombing is the latest in a string of chemical attacks on Syrian city

UN investigation found that Syrian Air Force and ISIS have used chemical weapons

This story contains graphic images, including some of child victims.

(CNN) More than 80 people were suffering severe breathing difficulties in Syria's embattled city of Aleppo after another chemical attack Tuesday on a rebel-held neighborhood, said the Syrian Civil Defense, a volunteer rescue group.

The UK-based Syrian Observatory for Human Rights also reported the attack, saying that medical sources accused regime warplanes of pounding the Sukkari neighborhood with barrel bombs "laden with poison gas."

This still from a video shows a girl treated at a makeshift hospital after what a rescue group called a chemical attack on her Aleppo neighborhood.

Harrowing footage distributed by the Syrian Civil Defense -- also known as the White Helmets -- shows small children and other victims being rushed to the makeshift Basel Aslan hospital in the arms of rescuers, gasping desperately for air as they are given oxygen masks.

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