MARGARET WARNER: President Obama expressed heightened concern about the situation in Syria in his first extended remarks about the possible use of poison gas by the Syrian government. His comments came as the humanitarian crisis there hit what the U.N. called a shameful milestone.
And a warning: Some viewers may find images in this story disturbing.
The president said today that Wednesday's alleged chemical attack outside Damascus, which killed an estimated 500 to more than 1,000 men, women and children, was -- quote -- "a big event of grave concern."
PRESIDENT BARACK OBAMA: That starts getting to some core national interests that the United States has, both in terms of us making sure that weapons of mass destruction are not proliferating, as well as needing to protect our allies, our bases in the region.
MARGARET WARNER: But, in an interview with CNN, Mr. Obama also sounded notes of caution about the U.S. taking immediate military action against the Syrian regime.
BARACK OBAMA: If the U.S. goes in and attacks another country without a U.N. mandate and without clear evidence that can be presented, then there are questions in terms of whether international law supports it, do we have the coalition to make it work? And, you know, those are considerations that we have to take into account.
MARGARET WARNER: U.N. inspectors were already on the ground in Syria when Wednesday's rocket attack occurred, investigating allegations of previous chemical attacks by Syrian President Bashar al-Assad.
Today, Syria's key ally Russia joined an international chorus calling for Assad to grant those U.N. inspectors access to Wednesday's site. In South Korea, U.N. Secretary-General Ban Ki-Moon called for thorough, impartial and prompt investigation, and said that those determined responsible would be held accountable.
BAN KI-MOON, United Nations: Any use of chemical weapons anywhere by anybody under any circumstances would violate international law. Such a crime against humanity should result in serious consequences for the perpetrator.
MARGARET WARNER: Back in the region, twin car bombs exploded outside two mosques in the northern Lebanese city of Tripoli, near the Syria border, killing at least 27 and leaving hundreds more wounded.
The Syrian conflict has reignited sectarian tensions in Lebanon, as well as strained the small country's resources as hundreds of thousands of Syrians seek safety within its borders. With more than 700,000 registered refugees, Lebanon is home to the most displaced Syrians.
But both Jordan and Turkey have accepted about half-a-million refugees. And Egypt and Iraq are each hosting more than 100,000. With the completion of this pontoon bridge over the Tigris River, Iraq in particular has seen a dramatic influx in recent weeks. The U.N. says the total number of Syrian refugees from the more-than-two-year conflict is now approaching two million.
Today, it announced that the number of Syrian children who've been forced to flee their country has reached a new milestone.
YOKA BRANDT, UNICEF: Last year around this time, we had 70,000 Syrian refugee children. Today, we have reached one million. And that tells us something about the escalation of this crisis.
MARGARET WARNER: At the Zaatari refugee camp in Jordan, home to 130,000 displaced Syrians, some of those children said they just want to go home.
CHILD (through interpreter): All I wish is that Syria could become peaceful again. That's all I want, for the trouble to stop. This time next year, I hope everything goes back to normal, to the way it used to be.
CHILD (through interpreter): I want to return to Syria, to live in peace and to go back to school. I want to be able to play with my old friends again, just like before. I want our country to be safe, safe enough to live in and for it to be prosperous again.
MARGARET WARNER: It is believed another two million children have been displaced inside Syria.