Nato Secretary general Anders Fogh Rasmussen warned that the use of chemical weapons in Syria was "unacceptable and cannot go unanswered".
He said: "Information available from a wide variety of sources points to the Syrian regime as responsible for the use of chemical weapons in these attacks. This is a clear breach of longstanding international norms and practice."
The prospect of a US and UK military intervention in Syria appears increasingly likely, but what would an attack by western forces involve?
A textile factory in Damascus has started producing gas masks in case of a repeat of a suspected chemical attack on the area.
Western countries including the UK are considering their response to Syria as evidence of a large-scale chemical attack in Damascus mounts.