The United Nations Security Council has called for clarification concerning an alleged chemical weapons attack in Syria.
At an emergency closed-door meeting, the divided Security Council backed an "impartial and prompt" investigation of the incident.
But the council did not say explicitly whether this should be carried out by UN experts currently in Syria.
Reports say Russia and China opposed calling for an immediate UN-led probe.
Syrian opposition activists say the early August 21 attack in Damascus suburbs may have killed upward of 1,300 people.
Video and other images distributed by opposition supporters – whose authenticity could not be independently confirmed – showed scores of victims, including many children.
Some experts said sarin gas may have been involved. But it was not immediately known what toxic substances may have been used.
The Syrian government has rejected allegations it was responsible.
The United States and its allies have called for the UN experts currently in Syria to probe the incident urgently.
Russia, an ally of the Syrian government, has questioned the circumstances of the incident, suggesting it could have been a rebel "provocation.”
UN Deputy Secretary-General Jan Eliasson said he was hopeful the UN experts now in Syria would be able to visit the site of the alleged gas attack. But there has been no indication that the Syrian government would assist in helping the team visit.
Eliasson said UN Secretary-General Ban Ki-moon was shocked over the incident, and called it a “serious escalation” in the two-and-a-half year-old Syrian war.
"This represents, no matter what the conclusions are, a serious escalation with grave humanitarian consequences and human consequences," Eliasson said.
Syrian Information Minister Omran Zoabi denied any involvement in the attack by the government, instead accusing rebel forces of “fabricating” the incident following successful operations by government troops.
"Everything that has been said is absurd, primitive, illogical, and fabricated." Zoabi said. "What we say is what we mean: there is no use of (chemical weapons) at all, at least not by the Syrian army or the Syrian state, and it's easy to prove."
The UN team currently in Syria has a mandate to investigate allegations of previous chemical weapons use in the conflict. Both sides have accused each other of using the weapons.
U.S. President Barack Obama has previously said the use of chemical weapons by President Bashar al-Assad's forces would be a "red line" that could lead to greater U.S. intervention.
In June, the Obama administration announced it believed the Syrian government had used chemical arms, killing scores of people, and said it would increase American aid to rebel forces.
Based on reports from AP, AFP and Reuters