"We wish here to state categorically that we have never used chlorine or any other toxic chemicals during any incidents or any other operations in the Syrian Arab Republic since the beginning of the crisis and up to this very day," Deputy Foreign Minister Faisal Moqdad told the annual meeting of the Organisation for the Prohibition of Chemical Weapons.
Damascus's denial comes as a growing number of countries including the European Union, the United States and Canada have cast doubt on whether the Syrian regime is truly making efforts to destroy its lethal arms.
"These uncertainties lead to doubts as to compliance by Syria with its obligations under the Convention," Bylica said at the opening of the five-day assembly in The Hague.
This "makes it impossible to have confidence that its chemical weapons programme has been irreversibly dismantled," Bylica said.
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Last week the OPCW itself voiced "grave concern" at the continued use of toxic arms in Syria.
The OPCW investigations did not directly blame any of the parties in the four-year civil war, aimed at ousting Assad and in which civil groups say more than 250,000 people have been killed.