British military scientists have found forensic evidence that chemical weapons have been used in the conflict in Syria, the Times newspaper says.
A soil sample thought to be from an area close to Damascus that was smuggled into Britain has provided proof that "some kind of chemical weapon" had been fired, it quoted defence sources as saying.
The tests were carried out at the Ministry of Defence's chemical and biological research establishment at Porton Down, the newspaper said.
Diplomats at the United Nations said some countries had "hard evidence" that chemical weapons have been used at least once in the Syrian conflict, without giving details.
The British team were unable to tell if the weapons had been fired by President Bashar al-Assad's regime or by the rebels fighting him, nor could they say if there had been widespread use, the Times said.
It cited an unnamed source as saying: "There have been some reports that it was just a strong riot-control agent but this is not the case - it's something else, although it can't definitively be said to be Sarin nerve agent."