The United Nations has called on the Syrian government to allow weapons inspectors to investigate claims of a chemical attack "without delay."
In a statement on Thursday, U.N. Secretary-General Ban Ki-moon confirmed he had asked that a team of experts be granted access to the Damascus suburb where a chemical weapons attack is alleged to have taken place.
Opposition activists have accused the regime of Syrian President Bashar al-Assad of killing hundreds of people in the incident, with many of the victims thought to have been women or children.
The Syrian National Coalition has said that more than 1,300 people lost their lives as a result of the deployment of nerve gas. Photographs purportedly taken from the scene show dozens of people foaming at the mouth and bodies stacked up in morgues.
If confirmed, the attack would seemingly cross President Barack Obama’s "red line." But some observers have suggested that despite warning of further intervention in the event of a chemical attack, the U.S. would still be unwilling to enter the conflict directly.
The White House has said that it is "deeply concerned" over the reports of chemical warfare, with administration spokesman Josh Earnest demanding that inspectors be given "immediate access to witnesses and affected individuals."
On Thursday, the U.S. State Department said it was "unable to conclusively determine" the use of chemical weapons. Obama, meanwhile, directed U.S. intelligence agencies to urgently gather information to verify the reports, the White House said.
In a bid to get evidence from the site of the alleged attack, Ban announced that he had formally asked the Syrian government -- which has denied deploying nerve gas -- to allow chemical weapons inspectors into Damascus.
"The secretary-general believes that the incidents reported yesterday (Wednesday) need to be investigated without delay," a statement from Ban's spokesperson said.
"A formal request is being sent by the United Nations to the government of Syria in this regard. He expects to receive a positive response without delay."
The U.N. team, led by Swedish scientist Ake Sellstrom, is currently looking into three claims of chemical use in the Syrian civil war. In total, the international body has received 14 reports of potential chemical attacks -- one issued by the Syrian government and the rest by Western governments.
As well as issuing a request directly to the Syrian government, Ban instructed Angela Kane, the U.N.'s high representative for disarmament affairs, to travel to Damascus in support of a proposed visit by the weapons inspectors.
Meanwhile, the U.N. high commissioner for human rights, Navi Pillay, said Thursday that reports of a chemical attack were "a matter of utmost urgency."
"These allegations are exceptionally grave and need to be comprehensively proved or disproved as soon as is humanly possible," she said.
Pillay added that her staff in the region had been told by well-placed sources inside Syria that in addition to those killed, there remained thousands of injured people in desperate need of medical care.
If confirmed, the predawn attack on Wednesday would represent the world's most lethal chemical weapons assault since the 1980s. It has led to angry demands for international action by opponents of Assad's regime and outside observers.
Prior to the U.N. statement on Thursday, France said the international community would need to respond forcefully if allegations that the Syrian government was responsible for a chemical attack on civilians proved true.
"There would have to be reaction with force in Syria from the international community, but there is no question of sending troops on the ground," Foreign Minister Laurent Fabius told the French television network BFM.
If the U.N. Security Council could not make a decision, one would have to be taken "in other ways," he said, without elaborating.
Likewise, Turkish Foreign Minister Ahmet Davutoglu said a "red line was crossed" in Syria and called for international action over the alleged attack.
"We call on the international community in this situation, where the red line was crossed long ago, to intervene as soon as possible," he said in Berlin after talks with his German counterpart, Guido Westerwelle.
Al Jazeera and wire services