BEIRUT, Lebanon — One of the worst chemical bombings in Syria turned a northern rebel-held area into a toxic kill zone on Tuesday, inciting international outrage over the ever-increasing government impunity shown in the country’s six-year war.
Western leaders including President Trump blamed the Syrian government of President Bashar al-Assad and called on its patrons, Russia and Iran, to prevent a recurrence of what many described as a war crime.
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Since then, the organization, working with the United Nations, has found that the Syrian government used chlorine gas as a weapon three times in 2014 and 2015, violating the treaty. Rebel fighters, doctors and antigovernment activists say there have been numerous other chlorine attacks, including at least two in the past week, in one case killing a doctor as he worked.
The Organization for the Prohibition of Chemical Weapons has also accused the Islamic State of using banned mustard gas in Iraq and Syria. The area around Khan Sheikhoun is not held by the Islamic State, but by other insurgents: Qaeda-linked militants and a variety of other rebel groups.
A chemical weapons attack, if carried out by the government, would be a brazen statement of impunity, coming during a major international meeting in Brussels where officials are debating whether the European Union and other countries will contribute billions of dollars for reconstructing Syria if it is presided over by a government run by Mr. Assad.
