UNITED NATIONS - Two cylinders reportedly seized by Syrian government troops in an area controlled by armed opposition groups contained deadly sarin, UN Secretary-General Ban Ki-moon said in a letter to the UN Security Council published on Monday.

Ban said that on June 14, the Organization for the Prohibition of Chemical Weapons (OPCW) United Nations Joint Mission overseeing the destruction of Syria's chemical stockpile analyzed the contents of the cylinders.

"The Joint Mission confirmed that these contained sarin," said Ban's letter. The letter said the cylinders were "reportedly seized by the armed forces of the Syrian Arab Republic in August 2013 in an area reportedly under the control of armed opposition groups."

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