Syria has agreed to allow UN inspectors to visit three sites to investigate accusations of chemical weapons use.

The UN said inspectors would travel to Syria to investigate three of the reported incidents, including Khan al-Assal, as soon as possible.

The United Nations did not identify the other two locations to be visited by investigators.

The head of a UN chemical weapons investigation team, Ake Sellstrom, and the head of the UN Office of Disarmament Affairs, Angela Kane, visited Damascus last week at the invitation of the Syrian government to discuss access.

Damascus had refused to let UN investigators go anywhere except Khan al-Assal in Aleppo province, where Syrian President Bashar al-Assad's government and its ally Russia say rebels used chemical weapons in March.

UN Secretary General Ban Ki-Moon has insisted that his team be permitted to visit at least one other location, the city of Homs, site of an alleged chemical attack by government forces in December 2012.

Both sides deny using chemical weapons.

The United Nations has received 13 reports of alleged chemical weapons use in Syria.

The UN investigation will only try to establish if chemical weapons were used, not who used them.

The United Nations says more than 100,000 people have been killed since Syria's civil war erupted, pitting Mr Assad's forces against rebels seeking to end his family's four-decade rule.

Nearly 1.8 million Syrians have fled the country - two-thirds of those since the start of the year - and more than 4.2 million people have been internally displaced, the United Nations has said.

Most of those in need are women and children.