NEW : 100 killed , it says . United Nations says there are more than 200 Syrian casualties . The rebel claim of capturing the city is called ' significant ' by the U.S. Brahimi : As the civil war rages , world leaders want to ensure chemical weapons are secure .
NEW : 100 killed , it says . United Nations says there are more than 200 Syrian casualties . The rebel claim of capturing the city is called ' significant ' by the U.S. As the civil war rages , world leaders want to ensure chemical weapons are secure .