At least 15 boys were killed when Syrian forces dropped a barrel bomb on a mosque operating as a makeshift school in Aleppo , the opposition Syrian Coalition said Wednesday . Barrel bombs are drums packed with explosives and shrapnel , which are then dropped from the sky . Tuesday 's attack is the second barrel bomb raid in two days in the northern Syrian city , which has become a flashpoint of the country 's civil war . `` Each and every day that the barrel-bombing of Aleppo continues , the Assad regime reminds the world of its true colors , '' U.S. Secretary of State John Kerry said in a statement after the attack . `` Each and every barrel bomb filled with metal shrapnel and fuel launched against innocent Syrians underscores the barbarity of a regime that has turned its country into a super magnet for terror . '' Later , Kerry defended U.S. policy toward Syria in an exclusive interview on CNN 's `` The Lead with Jake Tapper . '' However , he did not dispute entirely a U.S. intelligence assessment that Syrian President Bashar al-Assad has regained some footing since agreeing to turn over chemical weapons to the international community to avoid possible military action against his regime . `` It 's fair to say that Assad has improved his position a little bit , yes , '' Kerry said . `` But he 's still not winning . This is a stalemate . '' Barrel bomb toll . On Monday , 26 people were killed , the UK-based Syrian Observatory for Human Rights said . And over the weekend , barrel bombs killed 126 people there . `` The mosque was being used as a school after all schools in the area were either hit or brimming with internally displaced civilians , '' Khalid Saleh of the Syrian Coalition said about Tuesday 's attack . `` Giving up on learning was not an option for these children , but the hatred of the Assad regime was blind enough to deprive them not only from their right to education but also from their right to live . '' Opinion : A terror group too brutal for al Qaeda ? 'Children , there are children ' Opposition groups have blamed the attacks on al-Assad . The Syrian government has previously said that military operations are targeting `` terrorist groups '' in neighborhoods of the city . Videos posted online after the attack on the Othman Bin Affan mosque Tuesday showed angry residents , arms raised to the sky , cursing at al-Assad . `` Children , there are children , '' some shouted . One man , standing in front of a child 's body , sobbed , `` Oh God , we 've had enough . '' `` Why us , '' a child told an activist who filmed the aftermath of the attack . `` We are not rebel fighters , we are children . '' CNN can not independently verify the death tolls or the authenticity of the videos . The United Nations says more than 100,000 people have been killed in Syria since fighting began in 2011 . Report : Syria to ship toxic agents . 90 killed in punishing air raids in Syria 's Aleppo . Al Qaeda 'disowns ' affiliate , blaming it for disaster in Syria .
Barrel bombs are drums packed with explosives and shrapnel . 26 people were killed Monday ; 126 over the weekend . `` Oh God , we 've had enough , '' one man sobbed . Kerry says al-Assad has strengthened his hand , but he 's `` still not winning ''