200 people have been killed across Syria on Thursday , an opposition group says . The Syrian Observatory for Human Rights said at least 20 were killed in the town of Rastan, which is located near Damascus and has a large Christian population. Helicopter gunships flew over Aleppo and Damascus , opposition activists say . At least one rebel fighter was killed , the group said . `` They must stop fighting and killing people now , '' U.N. secretary-general says .
200 people have been killed across Syria on Thursday , an opposition group says . The Syrian Observatory for Human Rights said at least 20 were killed in the town of Rastan, which is located near Damascus and has a large Christian population. Helicopter gunships flew over Aleppo and Damascus , opposition activists say . `` They must stop fighting and killing people now , '' U.N. secretary-general says .