In this citizen journalism image provided by Edlib News Network, ENN, a Syrian girl holds a sign during a demonstration in Maaret Al-Numan, Idlib province, northern Syria. More than 100,000 Syrians have been killed since an uprising against Syrian President Bashar Al-Assad erupted in 2011. — AP BRUSSELS — NATO's chief says he is convinced that the Syrian government used chemical weapons against its people and insists a strong reaction is needed to show dictators around the world that such weapons cannot be used with impunity. “Personally, I am not only convinced that a chemical attack has taken place ... I am also convinced that the Syrian regime is responsible,” NATO Secretary-General Anders Fogh Rasmussen said on Monday when asked if he had seen intelligence to prove Assad was behind the suspected attack which left hundreds dead. “In general, we have concrete information,” he said. Rasmussen stressed repeatedly that the international community could not allow the use of chemical weapons go by unchallenged but he was guarded about any military response. “The aim of the response should be to send a very clear message ... that you cannot do that without a very firm international reaction,” he told a regular news conference. Any military action, however, “would be very short, sharp, tailored,” Rasmussen said, adding: “I don't see a long-term, sustainable military solution in Syria ... we need a political process.” It would be up to NATO's 28 members, led by the United States, to decide what specific military response they might make, he said. “I don't envisage any further NATO role” beyond providing a forum for consultations and backing up member Turkey which shares a tense border with Syria, he added. Meanwhile, observers are saying that the West's inaction days after threats to launch punitive action against Syria for a deadly chemical weapons attack could badly damage its credibility in tackling other global flashpoints. “Once Lebanon and Syria and Egypt trembled when Washington spoke. Now they laugh,” observer Robert Fisk wrote in British newspaper The Independent. “No one in the Middle East takes America seriously anymore,” he wrote. French President Francois Hollande appears resolute in his resolve to “punish” Damascus. – Agencies