NEW : An opposition group claims 72 deaths ; Russian news says ` ` terrorists '' targeted . Syria : Syrian official says ` ` those who lead the aggression '' will pay the price . Russia 's government links a rebel group to March chemical attack in Syria . Russian government says the evidence for a U.N.-backed strike should be undeniable .
NEW : An opposition group reports 72 deaths ; state news says `` terrorists '' targeted . NEW : Syrian official says `` those who lead the aggression '' will pay the price . Russia 's government links a rebel group to March chemical attack in Syria . Russian leader says the evidence for a U.N.-backed strike should be undeniable .