The video is graphic and disturbing. Medical teams are seen desperately scrambling to save dozens of lifeless adults and young children. There is no sign of blood or bullet wounds. All have apparently suffocated.

The Syrian opposition says the footage shows a chemical weapons attack in Damascus early Wednesday. They say hundreds have died, including many young children, in a poison gas bombardment by the Syrian army in the Damascus suburb of Ghouta.

"Over 650 confirmed dead result of deadly chemical weapon attack in Syria," says a Tweet from the opposition Syrian National Council. A British group, The Syrian Observatory for Human Rights, says more than 100 were killed.

As common in circumstances like this, the video cannot be verified. The death toll cannot be substantiated. But there is nothing about the video that looks fake. The images of lifeless, nearly naked men, women and children shows some dead, some clinging to life and others twitching.

The official Syrian government news agency dismissed the claims, saying "reports on the use of chemical weapons in Ghouta are totally false."

Image from myfreearbeen via bambuser.com

But Britain's Foreign Secretary, William Hague, is among those expressing alarm. "These reports are uncorroborated and we are urgently seeking information," he said. "But it is clear that if they are verified, it would mark a shocking escalation in the use of chemical weapons in Syria."

All of this is happening as a team of U.N. inspectors arrives in Syria to investigate three previous claims of chemical weapon use near the northern city of Aleppo. It has taken months for the U.N. to negotiate access. The British Foreign Secretary called on the Syrian government to give the U.N. inspection team immediate access to the Damascus suburb where today's attack is said to have taken place.