Around 100 people are injured after what Syrian officials say was a chemical attack on the government-held city of Aleppo.

There's been some back and forth about what happened.

Aleppo's chief of police told state-run Syrian Arab News Agency that terrorist organizations targeted  residential neighborhoods  Saturday night with shells that contained toxic gas.

But a Turkish-backed organization of Syrian rebel groups told Al Jazeera  the government was trying to frame it  and denied that it even had poisonous gas.

Footage from SANA shows people being treated in hospitals following the apparent chemical attack.

Officials pointed out that chlorine gas was likely used due to some symptoms victims exhibited.

A team working with the U.N.  has accused  both the Syrian government and militant groups of using chlorine gas and other chemical weapons in the past.

In response to the suspected gas attack on Aleppo, Syrian-allied Russian warplanes launched airstrikes on rebel-held areas in northern Syria for the first time in months.

The attack violates  terms of a truce  between Turkey and Russia, which was struck at a summit back in September.