Most of those killed were ISIS fighters , according to the Syrian government . 302 Syrian Kurdish fighters also died in battles with ISIS , it says . Most of the dead were civilians ; two of them were beheaded , Syrian government says .
481 of those killed were ISIS fighters , according to the Syrian Observatory . 302 Syrian Kurdish fighters also died in battles with ISIS , group says . 21 of the dead were civilians ; two of them were beheaded , Syrian Observatory says .