美国有线新闻 CNN 疑云再现 叙利亚一小镇疑遭化武袭击（在线收听）

Our first story, there's been an apparent chemical weapons attack in the Middle Eastern nation of Syria. We've been covering the country's civil war for years. It started in 2011. The United Nations estimates that 400,000 Syrians have been killed and millions have fled their homes.

What made Thursday's attack so horrible, even in this war-torn country, was that it reportedly involved a poisonous gas, according to multiple activist groups in the country.

Witnesses say it killed dozens of people, including families, though there have been different reports on exactly how many people died. Hundreds have been injured. Doctors say the victims had breathing problems, pale skin, sweating, narrow pupils, all symptoms of a chemical attack.

It happened in a western Syrian city that's held by rebels who are fighting the government. Activist groups say the attack was carried out by Syria's government. It's been blamed for previously using chemical weapons in the war.

Syrian government forces said yesterday, they categorically denied using chemical weapons in the area and that they held terrorist groups and their supporters responsible.

Leaders from all over the world gave enraged responses yesterday to the apparent chemical attack.

JIM SCIUTTO, CNN CHIEF NATIONAL SECURITY CORRESPONDENT: Chemical weapons are known as the "poor man's atom bomb", because at relatively little cost, they could have devastating effect, both in terms of casualties, but also in the sheer horror of the injuries and the sheer fear of contamination.

In the history of warfare, they've been used very seldom. You have to go back to World War II for widespread use, although Saddam Hussein used them in the late 1980s, killed some 5,000 people in northern Iraq, in Kurdistan. More recently, the Assad regime has used them repeatedly in the war in Syria. It's estimated, some 1,500 people have been killed, 15,000 injured in chemical weapons attacks in Syria.

The Geneva protocol of 1925 banned the use of chemical weapons in warfare, but not the production. It wasn't until the early 1990s that the Chemical Weapons Convention banned the production and stockpiling as well. And since then, some 90 percent of the world's chemical weapons have been destroyed.

But still, to this day, there's a lot out there in 17 countries still have them. From the ones you'd expect, North Korea for instance, which did not sign on to any of those treaties, but also the U.S., although the U.S. has committed never to use them in warfare and is committed to destroy all of them by the 2020s.