French Foreign Minister Laurent Fabius said Monday a UN report proving that poison gas killed hundreds in last month\'s Syria attack left \"no doubt\" President Bashar al-Assad\'s regime was responsible for the incident. \"The content of the report is damning and confirms massive use of sarin gas... It all leaves no doubt on the origin of the attack,\" Fabius said on RTL radio, adding the report \"reinforced the position of those who said the regime was guilty.\"