Today could go down in history as the day that changed everything -- -- it's already killed over a 100000 people in Syria hundreds more dead many of them children. But this time it appears deadly... See More
Today could go down in history as the day that changed everything -- -- it's already killed over a 100000 people in Syria hundreds more dead many of them children. But this time it appears deadly chemical weapons were used although that hasn't been verified. Potentially one of the worst war atrocities in recent memory. We Egypt also on the brink of civil war this could be a turning point not just for Syria but for the Arab Spring as we know -- Our chief global affairs correspondent Martha Raddatz is there. As a note to our viewers this important story includes incredibly graphic and disturbing images. The in -- our gut wrenching. Body's role to cross clinic floors many of the victims children even infants. Others still fighting for life rescuers trying to resuscitate him. Victims practically gasped for air lips turned blue their body showed no other outward signs of injury no plot. The convulsions that we've seen a number of people and I'm babies. Pinpoint people's. Garrett -- -- is sometimes it easy she consistently some sort of nerve agent poisoning. The rebels fighting the Asad regime say Syrian government troops fired rockets on these innocence. Rockets carrying poisonous gas. The images are impossible to verify -- for certain. And the Asad regime denies that poison gas was used calling the claims baseless. But this weapons expert says the videos show clear signs. It's the only explanation I can really -- -- this is this looks like. The studies and sort of being have been destroyed since he bought something like -- -- If verified this would be one of the deadliest chemical attacks in decades. The Syrian opposition claiming over a thousand killed. But the estimates vary while there is still a question about the veracity of the claims of chemical weapons use. The -- Gordon is not doubt that the video is real. I think the amount of children and babies who law to -- in to all right I didn't think you can get children faith that. In my opinion saw it. That's the -- -- -- I think case is very -- I'd be very surprised if it turned out via take. UN chemical weapons inspectors -- -- Syria earlier this week. To investigate allegations of previous chemical weapons use but today the US and other nations condemned this suspected attack. And called for an urgent meeting of the united nations Security Council to investigate. This -- cents a no -- about -- what the conclusions are. The serious escalation there is. Work that can be done with our international partners to try to continue to pressure the Asad regime. I -- we've seen evidence and indications that the -- regime is feeling that pressure. But your right that we have not it is not resulted in the outcome that we would like to see which is aside being completely removed from power. But the White House is -- that before. Almost a year to that day President Obama warned Syria not to cross that red line. We have been very clear to the outside -- regime but also to. Other players. On the ground. That. A red line for us is. We start saying. A whole bunch chemical weapons moving around -- being -- -- that would change my calculus that would change my question. The estimated casualties since two days suspected attack. Far exceed previous suspected chemical attacks linked -- -- -- government. The most deadly of which was in March when at least thirty were killed. This is -- a matter of cooperation but so far US aid to Syrian rebels has been -- to -- What kind of military aid is getting to Syria from the US right now. Is actually on the US military said the Department of Defense besides which the assistance with the humanitarian relief effort were also. Engaged in. Training of our Jordanian partners. As you know we've got military planners in Jordan. To have small arms arriving are now the Department of Defense is not engaged in -- and arming the opposition. In no way are we giving them any kind of -- not small arms not guns not weapons the Department of Defense is not. The uprising in unrest in Syria has already become a two year long civil war. With around 100000. Dead. Millions of Syrian refugees have already fled the civil conflict. Just two and a half years after the end of the Arab Spring. Unrest continues to built the neighboring Middle East countries from Iraq to Libya. In less than 400 miles away each continues to sit on the brink of civil war. Big gains that the Arab Spring now in question. In the past week alone more than 1000 people have died and thousands more injured. The military's intervention sparked outrage across the world and in the US. I spoke with Egypt's interim prime minister house of -- -- yesterday. Where do you see this. And I'm -- is to prepare of this country for and -- and democratic regime. We want to have a constitution. A -- -- new constitution. Open. Was -- indeed -- some principals would put it to overcome them. In Cairo today government forces are trying to downplay the violent images we saw all last week. What would you say to Americans about Egyptian about Egypt's security forces. I invite them to county tendency -- armed forces trying to secure the country. Against editors that they can -- -- -- for -- With all that has happened in Cairo over the past few months. It's hard to imagine any more fuel added to the fire. But any hour now former President Hosni Mubarak is set to be released from prison in Cairo. When Mubarak walks out of Cairo's Tora prison. He won't exactly be a free man prime minister Bob -- we just ordered Mubarak to be placed under house arrest upon his release. Reaction on the street was -- And this is horrible. -- cancel everything. We've been through on the killing all the bloodshed since devastate the demands that we have been fighting for. I don't see any -- I've -- minutes. Another sign that the hopes of the Arab Spring. Trampled in the dust for Nightline I'm Martha Raddatz in Cairo. The UN Security Council is called for an emergency session. In light of the attack.
This transcript has been automatically generated and may not be 100% accurate.