By Michelle Nichols
UNITED NATIONS (Reuters) - U.N. inspectors will travel to Syria "as soon as possible" to investigate claims of chemical weapons use during the country's civil war after President Bashar al-Assad's government granted access to three sites, the United Nations said on Wednesday.
The head of a U.N. chemical weapons investigation team, Ake Sellstrom, and the head of the U.N. Office of Disarmament Affairs, Angela Kane, visited Damascus last week at the invitation of the Syrian government to discuss access and obtained an understanding that it would be granted.
"The mission will travel to Syria as soon as possible to contemporaneously investigate three of the reported incidents, including Khan al-Assal," U.N. Secretary-General Ban Ki-moon's press office said in a statement.
The Syrian government, backed by its ally Russia, accused rebels of using chemical weapons in Khan al-Assal in Aleppo province in March. The United Nations did not identify the other two locations to be visited by investigators.
Ban appointed Sellstrom at the end of March to investigate the Khan al-Assal complaint, as well as claims by Britain and France of chemical weapons use elsewhere in Syria, where a two-year revolt has descended into civil war.
But diplomatic wrangling and concerns over safety have prevented Sellstrom and his team of experts from entering Syria. The United Nations has been demanding unfettered access to conduct the chemical weapons investigation.
The United Nations says it now has 13 reports, mostly from Britain, France and the United States, of chemical weapons attacks. The Syrian government and the opposition both deny using such weapons. The U.N. inquiry will only try to establish if chemical weapons were used, not who used them.
"The Secretary-General remains mindful of other reported incidents and the mission will also continue to seek clarification from the member states concerned," the U.N. statement said.
The United States concluded last month that Assad's forces used chemical weapons against rebel fighters. President Barack Obama said last year that any attempt to deploy or use chemical or biological weapons in Syria would cross a "red line."
U.S. congressional panels this month agreed to a White House plan to provide arms to the Syrian rebels.
Syria is one of seven countries that has not joined the 1997 convention banning chemical weapons. Western countries believe it has stockpiles of undeclared mustard gas, sarin and VX nerve agents.
Earlier this month, Russia's U.N. envoy Vitaly Churkin sharply criticized what he described as Western nations' "small propaganda storm in a glass of water" over allegations that the Syrian government has used chemical weapons.
Damascus had been refusing to let U.N. investigators go anywhere except Khan al-Assal. Ban had insisted that Sellstrom's 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.
Rebels seized Khan al-Assal from Assad's forces last week. Syrian state media accused insurgents on Saturday of killing 123 people, the majority of them civilians, during the offensive.
A senior Western envoy said that Syrian opposition leaders, who met informally with the U.N. Security Council on Friday, had pledged to grant to chemical weapons experts access to areas they controlled.
The United Nations says more than 100,000 people have been killed in the Syrian conflict.
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.
(Reporting by Michelle Nichols; Editing by Vicki Allen, Eric Beech and Philip Barbara)