UN Secretary-General Ban Ki-moon said on Wednesday that he was "shocked" by the reported use of chemical weapons on the outskirts of Damascus, the Syrian capital, reiterating that "any use of chemical weapons by any side under any circumstances would violate international humanitarian law."

"The secretary-general is shocked to hear the reports of the alleged use today of chemical weapons in the suburbs of Damascus," Eduardo del Buey, the deputy UN spokesman, said at a daily news briefing here.

The statement came as the UN Security Council is to have an emergency meeting on Syria at 3:00 p.m. EDT (1900 GMT) on Wednesday.

"The secretary-general is aware that a number of member states, the Arab League and the European Union have expressed grave concern about the most recent reports of the possible use of chemical weapons in Syria," del Buey said. "The secretary-general reaffirms his determination to ensure a thorough investigation of the reported alleged incidents that are brought to his attention by member states."

Ban reiterated that any use of chemical weapons by any side under any circumstances would violate international humanitarian law, he said.

The alleged attacks took place just two days after a group of UN inspectors began a probe into the alleged use of chemical weapons in the Syrian conflicts.

The Syrian opposition accused President Bashar al-Assad's forces of killing as many as 1,300 people in chemical weapon attacks in suburbs of Damascus on Wednesday, reports said. The Syrian government, however, denied the accusation.

The UN team of inspectors was set up at the request of the Syrian government in March and it is headed by Swedish expert Ake Sellstrom, former UN weapons inspector in Iraq.

The UN fact-finding group will investigate the alleged use of chemical weapons reported by the government of Syria at Khan al- Assal as well as two other allegations of the use of chemical weapons reported by member states.

The Syrian government and rebels blamed each other for a purported chemical weapons attack on Khan al-Asal on March 19 that killed at least 25 people and wounded 130 others.

According to the agreement reached in Damascus in July, the UN team and the Syrian government "are discussing, in parallel, other allegations and their related sites," del Buey said.

"The United Nations mission to investigate allegations of chemical weapons use in Syria is following the current situation in Syria carefully, and remains fully engaged in the investigation process that is mandated by the secretary general," he said.

"Professor Sellstrom is in discussions with the Syrian government on all issues pertaining to the alleged use of chemical weapons, including this most recent reported incident," del Buey said.

The Argentine UN mission, which holds the presidency of the UN Security Council for this month, said that the 15-nation Security Council would hold an emergency meeting on Wednesday afternoon to discuss the latest alleged use of chemical weapons in Syria.

The United States and several European countries have expressed fears that Syria's chemical weapons may "fall into the wrong hands" if the Syrian administration falls.

While Washington warns that the Syrian forces' use of chemical weapons would be "a red line," the violation of which would trigger military intervention, Damascus repeatedly stressed "even if we had such weapons, we would not use them," and alleged the rebels might use chemical bombs against civilians to frame the government.