Moscow, August 4 (RHC)-- Russia says it had warned the United States about the use of toxic shells by a U.S.-backed “moderate” militant group before the Tuesday attack that killed seven people and injured over 20 more in Syria’s Aleppo.

On Wednesday, Lieutenant-General Sergey Chvarkov, the director of the Russian Reconciliation Center in Syria, said the information was given to the U.S. on Monday, a day prior to the attack. The Russian Ministry of Defense also confirmed that the attack in Aleppo was launched by a Takfiri terrorist group.

Moscow has long insisted that the U.S.-backed, so-called moderate opposition groups in Syria should leave the areas held by terrorists. Washington claims it is unable to remove the opposition groups.

According to reports, the gas used in the attack was Chlorine, which is highly toxic and leads to respiratory problems and the loss of consciousness of those who come in contact with it.