The United Nations has said experts will travel to Syria as soon as possible to investigate three alleged chemical weapons attacks.
UN spokesman Martin Nesirky said the green light for the investigation followed last week's visit to Damascus by UN disarmament chief Angela Kane and the head of the chemical weapons investigation team, Ake Sellstrom, and "the understanding reached with the government of Syria".
Mr Nesirky said the experts will visit Khan Al-Assal outside Aleppo, which was under attack by government forces on Wednesday after its capture by rebels last week. The government and rebels blame each other for a purported March 19 chemical attack on the village that killed at least 30 people.
Mr Nesirky did not give any details of the other two incidents to be investigated.
A well-informed UN diplomat, speaking on condition of anonymity because discussions on the issue have been private, said Mr Sellstrom is expected to choose the two other sites based on the technical and scientific information the UN has received.
Syria initially asked Secretary-General Ban Ki-moon to investigate the Khan al-Assal incident and baulked at a broader investigation sought by the UN chief after Britain, France and the United States sent the UN information about a dozen other alleged attacks in Homs, Damascus, Aleppo and elsewhere.
Last week's Damascus visit by Ms Kane and Mr Sellstrom led to Syria's agreement to the investigation of three incidents. Mr Nesirky said "The secretary-general remains mindful of other reported incidents and the mission will also continue to seek clarification from the member states concerned."
The diplomat stressed that the chemical weapons experts should have access to all 13 sites.The mandate of the investigation team is to report on whether chemical weapons were used, and if so which chemical weapon, but not to determine the responsibility for an attack.
In June, the United States said it had conclusive evidence that Syrian president Bashar Assad's regime has used chemical weapons against opposition forces.
That crossed what President Barack Obama had called a "red line" and prompted a US decision to send arms and ammunition to the opposition, not just humanitarian aid and non-lethal material like armoured vests and night goggles.