Hundreds are said to be dead after what anti-regime activists in Syria are calling a government "poisonous gas" attack near Damascus. According to the rebels, forces loyal to President Bashar al-Assad fired "rockets with poisonous gas heads" in the outskirts and suburbs of the Syrian city.

Reports of deaths range from 100 to close to 800. If attack is confirmed, Wednesday's events would be the most violent since March 19, when 30 people were killed—an incident that Assad's regime and the rebels blamed on one another.

The Syrian government said that the allegations about Wednesday's poisonous gas attacks were false. Chemical weapons inspectors from the UN are in Syria investigating claims that chemical weapons have been used by both sides in this civil war.

The UK-based group, Syrian Observatory for Human Rights, says that they have documented at least 100 deaths after the attack on Wednesday. They say that shelling was violent, and couldn't confirm whether the deaths were from the shelling or toxic gas. The Local Coordination Committees estimate that a number closer to 800 were killed on Wednesday.

Horrific footage emerged yesterday on YouTube, showing activists, children, and other victims having convulsions, struggling to move and breathe. A nurse at a Duma medical facility, Bayan Baker, told Reuters: "Many of the casualties are women and children. They arrived with their pupils dilated, cold limbs and foam in their mouths." While the footage has not been fully authenticated, most sources indicate that the videos are genuine.

Britain's Foreign Secretary William Hague was one of the first international leaders to speak about the reports, saying that if they were verified, "it would mark a shocking escalation in the use of chemical weapons in Syria."

Unrest and uprisings began in Syria in early 2011. Since then, over 100,000 people have been killed in the civil war.

[image of Syrian refugees crossing into Iraq, via AP]