An emergency meeting of the U.N. Security Council Wednesday called for a prompt investigation into an alleged deadly gas attack by Syrian President Bashar Assad's forces that activists say killed hundreds of civilians outside Damascus, the Syrian capital. If confirmed, the attack would be the worst reported use of chemical arms in the two-year-old civil war, and would apparently cross what President Barack Obama has called a "red line."
"There is a strong concern among council members about the allegations and a general sense that there must be clarity on what happened and the situation must be followed closely," Argentina's U.N. ambassador current Security Council president, Maria Cristina Perceval, told reporters after a two-hour, closed-door emergency meeting of the council.
Al Jazeera's John Terrett, reporting from New York, described the statement released by the Council as "very vague, bland and tepid."
"The Security Council is hobbled on issue of Syria; they can't agree on anything," he said.
The United States and other Western and regional countries called for U.N. chemical weapons investigators -- who arrived in Damascus just three days ago -- to be urgently dispatched to the scene of what appears to be one of the deadliest incidents of Syria's war.
But Ake Sellstrom, who is heading the U.N. team in Syria, says a formal request from a member state would have to come through the U.N. channels and Syria would need to agree in order for the team to investigate the newest accusations.
U.N. diplomats, however, said Russia and China opposed language that would have demanded a U.N. probe.
Syria's ambassador to Russia also said Wednesday that information that government troops used chemical weapons near Damascus is not true. While Russian Foreign Minister Sergei Lavrov said the reported chemical attack could be a "provocation" but called for a "fair and professional" investigation into the claims.
The White House said Wednesday it was "deeply concerned" over the reports and that it would consult with other Security Council members. It also said it had no "independent verification" about the use of chemical weapons in Syria.
"We are formally requesting that the United Nations urgently investigate this new allegation," White House spokesman Josh Earnest said. "If the Syrian government has nothing to hide," he said, it would facilitate the work of the inspectors.
In June, the United States said it had conclusive evidence that Assad's regime used chemical weapons against opposition forces -- prompting a U.S. decision to begin arming rebel groups, although that has yet to happen.
Meanwhile, the Arab League echoed the call of the Security Council, asking that U.N. weapons inspectors already in the country be allowed to visit the site of the alleged new chemical weapons attack.
The government attacks reportedly took place in the Ghouta region, east of Damascus, in suburbs including Zamalka, Arbeen and Ein Tarma. The Syrian government denied that it had used chemical weapons.
Information Minister Omran Zoabi said the allegations were "illogical and fabricated." A Syrian military officer appeared on state television and said the allegations were untrue and a sign of "hysteria and floundering" by Assad's opponents.
A video purportedly shot in Kafr Batna, a suburb on the eastern outskirts of Damascus, showed a room filled with more than 90 bodies, many of them children, with a few women and elderly men. Most of the bodies appeared ashen or pale but with no visible injuries. About a dozen were wrapped in blankets.
"Many of the casualties are women and children. They arrived with their pupils constricted, cold limbs and foam in their mouths. The doctors say these are typical symptoms of nerve gas victims," a nurse at Duma Emergency Collection facility, Bayan Baker, said.
Exposure to sarin gas causes pupils in the eyes to shrink to pinpoint sizes and prompts foaming at the lips.
"The attack took place at around 3:00 a.m. (8 p.m. EST). Most of those killed were in their homes," Khaled Omar, of the opposition Local Council in Ein Tarm, east of Damascus, said.
The country's main opposition group, Syrian National Coalition, accused the regime of killing more than 1,100 people in the attacks on Twitter. From Istanbul, leading Syrian opposition figure George Sabra said the death toll from the attacks, including chemical weapons, stood at 1,300.
In a press conference Wednesday, Sabra accused the United Nations and the international community of hesitancy to take any action against the Syrian regime and called for a no-fly zone to be implemented as well as more military support for the rebels.
Timeline: History of chemical and biological warfare
Dr. Khaled al-Doumi, a doctor and manager of the medical center of Duma, a Damascus suburb near the site of the alleged attack, said, "Medically-speaking, the symptoms indicate that poisoning was a result of phosphorous compounds that could be caused by organic insecticides or sarin gas."
"There are people trapped at home who are unreachable so the death toll is going to soar up," al-Doumi said. A statement is expected from the medical center to announce the final figures in the attack.
Speaking to Al Jazeera from Finland, Paula Vanninen, professor and the director of Verifin, the Finnish Institute for Verification of the Chemical Weapons Convention, said that it was very difficult to see what actually happened to the victims from only studying videos.
"Some of those people were shaking and could have gotten the nerve agent exposure but for others it's quite difficult to say from the video what has caused their death. But you can see that they couldn't breathe. Something has caused that – they were killed by not being able to breathe anymore," she said.
"It's a horrible tragedy that should never have happened."
Vanninen said that people in videos of the attack's aftermath who were helping those who showed symptoms of a chemical attack should have had similar reactions if there actually were chemical agents used. However, she stated that those who helped may have shown symptoms later.
The professor added that the U.N. team should take samples as soon as possible -- and that chemical agents would be evident on biological samples and also environmental samples.
It would take the authorities at the Organization for the Prohibition of Chemical Weapons up to 14 days to report the results after they received samples, said Vanninen.
Meanwhile, Syrian government has long denied claims by the opposition on chemical weapons use, saying rebels fighting to overthrow President Assad's government have used such weapons.
Wednesday's claim of the chemical attack, if confirmed, would the most serious report to date in the conflict, surpassing the March 19 claim of the attack in Khan al-Assal when at least 30 people were reported killed. Assad's regime and the rebels have blamed each other for that attack.
The U.N. team is currently scheduled to probe three sites: the village of Khan al-Assal just west of the embattled northern city of Aleppo and two other locations, which are being kept secret for security reasons.
Syria is said to have one of the world's largest stockpiles of chemical weapons, including mustard gas and the nerve agent sarin. The government refuses to confirm or denies it possesses such weapons.
The unrest in Syria began in March 2011 and later escalated into a civil war. More than 100,000 people have been killed in the conflict so far, according to the U.N.
Al Jazeera and wire services