BEIRUT — Scores of men, women, and children were killed outside of Damascus on Wednesday in an attack marked by the telltale signs of chemical weapons: row after row of corpses without visible injury; hospitals flooded with victims, gasping for breath, trembling, and staring ahead languidly; images of a gray cloud bursting over a neighborhood.
But even with videos, witness accounts, and testimonies by emergency medics, it was impossible to know for certain how many people had been killed and what exactly had killed them. The rebels blamed the government, the government denied involvement, and Russia accused the rebels of staging the attack to implicate President Bashar Assad’s government.
Images of death and chaos poured out of Syria, marking what may be the single deadliest attack in more than two years of civil war. Videos posted online showed dozens of lifeless bodies, men wrapped in burial shrouds, and children, some still in diapers. Hospital scenes showed corpses and the stricken sprawled on gurneys and tile floors as medics struggled to resuscitate them.
Getting to the bottom of the strike could alter the course of the conflict and affect the level of the West’s involvement.
President Obama said almost a year ago that the use of chemical weapons was a red line. But the subsequent conclusion by the White House that the Syrian army had used chemical weapons did not bring about a marked shift in US engagement.
This latest attack, by far the largest chemical strike yet alleged, could tip that balance — as many foes of Assad hope it will.
But like so much in Syria, where the government bars most reporters and the opposition heavily filters the information it lets out — the truth remains elusive.
The attack was especially conspicuous given the presence in Damascus of a team sent by the United Nations to investigate chemical strikes reportedly waged earlier in the war.
The United States, the European Union, and other world powers called for the investigators to visit the site of the Wednesday attack.
The Security Council, meeting in emergency session, issued a statement calling for a prompt inquiry and a cease-fire in the conflict, but took no further action.
“I can say that there is a strong concern among council members about the allegations and a general sense that there must be clarity on what happened, and that the situation has to be followed carefully,” said María Cristina Perceval of Argentina, the president of the 15-member Council, after the meeting. “All council members agreed that any use of chemical weapons, by any side under any circumstances, is a violation of international law.”
In the opposition’s account of the deadly events, Assad’s forces deployed poison gas on a number of rebel-held suburbs east of Damascus, the capital. They described medics finding people dead in their homes.
Videos posted online showed mostly men and children, but the opposition activists said many women were killed too, but were not photographed, out of respect.
The actual death toll remained unclear. The Syrian Observatory for Human Rights said late Wednesday that more than 130 people had been confirmed dead in attacks around Damascus, though it could not confirm the use of gas. Other opposition estimates put the death toll at more than 1,000.
The video record posted online did not have enough detail to draw a full picture of what occurred. Unlike videos often uploaded by the opposition, the images Wednesday did not show the immediate aftermath of attacks in the communities.
The videos, experts said, also did not prove the use of chemical weapons, which interfere with the nervous system and can cause defecation, vomiting, intense salivation, and tremors.
Gwyn Winfield, editor of CBRNe World, a journal that covers unconventional arms, said the medics would likely have been sickened by exposure to so many people dosed with chemical weapons — a phenomenon not seen in the videos. He said that the victims could have been killed by tear gas used in a confined space, or by a diluted form of a more powerful chemical agent.