The United Nations said Thursday that it hoped chemical weapons inspectors would be in Syria within days to start an investigation into the alleged use of the banned weapons.

The United Nations announced on Wednesday that President Bashar al-Assad's government has agreed to let inspectors go to three sites where chemical arms attacks have been reported during the 28-month-old Syrian civil war.

"The team will depart for Syria as soon as practical and is preparing to depart within days," the UN spokesman Martin Nesirky told a briefing.

The experts are already gathering in The Hague, he added. They "will be ready to depart once the remaining logistical and legal details for the mission have been finalized."

Nesirky said that the head of the mission, Ake Sellstrom, would be accompanied by about 10 experts from the Organization for the Prohibition of Chemical Weapons (OPCW) and the World Health Organization (WHO).

Nesirky would not say how long the team expected to be in Syria.

The United Nations is also keeping confidential the site of two of the reported attacks "as a safety and security precaution," the spokesman added.

The sites are believed to be near Damascus and at Homs, according to diplomats.

It was announced on Wednesday that the inspectors would go to Khan al-Assal, near Aleppo.

The Assad government called for a UN inquiry after accusing opposition rebels of using chemical arms at Khan al-Assal on March 19. The government said at least 26 people, including 16 soldiers, were killed in the attack.

It refused entry to UN inspectors afterwards, however, because UN leader Ban Ki-moon demanded "unfettered" access to investigate all allegations of chemical weapons use.

The Syrian opposition has denied any role in the Khan al-Assal attack. Britain, France and the United States, which have sent evidence to the UN team, say they are sure only Assad's forces have used chemical arms in any attack.

Russia has backed the government claims that the rebels were behind the March 19 strike.

The UN says it has been given reports of 13 chemical arms attacks in all. Syria, where the conflict has left more than 100,000 dead, has a major stockpile of chemical arms.