UN inspectors will go to Syria to investigate three sites where chemical weapons attacks have been reported, the United Nations said Wednesday.
The Syrian government has blocked the inspectors since calling for a UN inquiry into the use of the banned arms in March.
"The mission will travel to Syria as soon as possible to contemporaneously investigate three of the reported incidents," said UN spokesman Martin Nesirky.
The announcement followed an accord reached with the Syrian government when two UN envoys went to Damascus last week.
According to diplomats, the inspectors are being assembled in Europe now and could go to Syria as soon as next week.
The UN says that Syria, Britain, France and the United States have informed it of 13 alleged chemical weapons attacks during the 28-month-old conflict.
While the initial inquiry will focus on three sites, Nesirky said UN leader Ban Ki-moon "remains mindful of other reported incidents and the mission will also continue to seek clarification from the member states concerned."
The spokesman said the first sites to be visited will include Khan al-Assal, near the Syrian city of Aleppo, where the government reported a chemical weapons attack on March 19. It said at least 26 people, including 16 government soldiers, were killed.
The government, and its ally Russia, have blamed Syrian rebels for the attack. The Syrian opposition says President Bashar al-Assad's forces staged the attack.
The other two sites to be visited by the inspectors are Ataybah near Damascus, where a suspected attack was staged in March, and Homs, where chemical weapons are alleged to have been used on December 23, diplomats said.
Britain and France have submitted evidence to the United Nations on the Ataybah and Homs attacks, which they say was carried out by the government.
The Syrian government called for the UN inquiry in March. But it then blocked the UN inspectors, insisting that they be limited to Khan al-Assal. Ban had demanded wider access for the investigation.
Ake Sellstrom, the Swedish expert in charge of the UN inquiry, and UN High Representative for Disarmament Affairs Angela Kane went to Damascus last week to negotiate the access accord.