200 people have been killed across Syria on Thursday , an opposition activist says . Turkey 's prime minister says it is considering plans for a buffer zone in northern Syria . Helicopter gunships fly over Aleppo and Damascus , opposition activists say . Undeterred by a wave of casualties , Syrian rebels say they will not back down in their quest to seize Aleppo , the country 's commercial hub and its second-largest city . ` ` They must stop fighting and killing people now , '' the secretary - general says .
200 people have been killed across Syria on Thursday , an opposition activist says . Turkey 's prime minister says it is considering plans for a buffer zone in northern Syria . Helicopter gunships fly over Aleppo and Damascus , opposition activists say . ` ` They must stop fighting and killing people now , '' the secretary - general says .