Western powers have demanded immediate access to the site of an alleged deadly chemical attack outside Damascus. A meeting of the United Nations Security Council has been called over the incident.
Britain, France and the United States prepared on Wednesday to make an official call for the investigation into chemical weapons use in Syria to be extended to the site of the latest alleged massacre.
Syria's opposition has accused forces loyal to Syrian President Bashar al-Assad of launching the attack - possibly using nerve agents - early on Wednesday. Videos that were distributed by activists showed medical staff attending to suffocating children. However, the validity of the footage has yet to be verified.
The Syrian opposition says that as many as 1,300 people were killed in the attack. A far lower estimate puts that number at 100. The opposition National Coalition called the alleged strike "a coup de grace that kills all hopes for a political solution in Syria."
The incident came as a 20-member UN chemical weapons team conducts an inspection of three sites where chemical weapons attacks allegedly took place.
Argentina, which holds the presidency of the Security Council, announced that the body would hold an emergency meeting at 1900 GMT to discuss the matter.
'Consistent with mandate'
The United States said there should be an investigation at the site. Washington is expected to be joined by Paris and London in asking for the investigation.
"Today, we are formally requesting that the United Nations urgently investigate this new allegation," said White House Deputy Press Secretary Josh Earnest. "The UN investigative team, which is currently in Syria, is prepared to do so, and that is consistent with its purpose and mandate."
Britain and France have drafted a letter to UN Secretary General Ban Ki-moon calling for the UN team to be given access to the site. Ban said he was determined to ensure a "thorough investigation."
UN chemical weapons inspector Ake Sellstrom was said to be in discussions with the Syrian government on Wednesday. The UN's press office said Sellstrom was involved in talks "pertaining to the alleged use of chemical weapons, including this most recent reported incident."
Russia also called for the matter to be investigated, but insisted that an attack, if proved to have happened, could also have been carried out by rebels.
rc/tj (AFP, dpa, Reuters)