Syria warned on Saturday that rebels could use chemical weapons in their fight against President Bashar al-Assad's forces, and insisted that the regime will never unleash such arms on its own people, AFP reported.
British Foreign Secretary William Hague, however, said there was evidence the Damascus government could actually employ chemical weapons stocks in the conflict which a rights group says has killed at least 42,000 people in nearly 21 months.
"Terrorist groups may resort to using chemical weapons against the Syrian people... after having gained control of a toxic chlorine factory" east of Aleppo, the foreign ministry said.
It added that Damascus would never use such weapons against its own people.
The ministry was believed to be referring to the Syrian-Saudi Chemicals Company (SYSACCO) factory near Safira, which was taken over earlier this week by militants from the jihadist Al-Nusra Front.
Syria "is defending its people against terrorism, which is supported by known countries, with the United States at the forefront," the ministry said.
Global concerns over Syria's chemical weapons stockpiles grew after US officials this week privately said the regime had begun mixing precursor chemicals that could be used for the lethal nerve agent sarin.
Some media reports said that the substance had been loaded into bombs for warplanes.
Hague said on Saturday there was evidence Syrian government forces could use chemical weapons against the insurgency.
"We are extremely concerned about the stockpiles of chemical and biological weapons, and we are also concerned about evidence during the last couple of weeks that the regime could use them," he told reporters in Manama on the sidelines of a security conference.
Hague said Britain had joined the United States in delivering a strong message to Assad's government and that the global community had "contingency plans concerning chemical weapons but will not disclose them."
He cited several "dangerous scenarios," including their "use by the regime" or falling into the hands "of other people."
Washington has said the use of chemical weapons would be a red line but that it fears rebel battlefield advances could prompt the regime to use them, or that stocks could fall into the hands of groups hostile to the US and its allies.