-- Dr. Nafie Abtan once operated a thriving medical clinic in Baghdad, but one day last June he received a hand-delivered letter threatening to cut his head off if he remained.
"We tell you to leave your job and to travel and to leave your hospital," the letter said.
Three days later, he did just that. He fled Iraq for neighboring Jordan, bringing with him his wife, Suhair, and young son, Moutaz.
Abtan and his family are like hundreds of thousands of other Iraqis who have fled their country amid the deadly violence that has wracked the nation and is creating what the international community calls a growing humanitarian crisis.
The United Nations estimates 700,000 Iraqis have fled to Jordan -- more than one-tenth the entire kingdom's population. As many as 1 million more Iraqis are estimated to have sought refuge in Syria, about 120,000 are in Egypt and 40,000 in Lebanon, according to the United Nations. (Watch Iraqis tell their stories )
Inside Iraq, another 1 million to 2 million people have been forced out of their homes as a result of the violence, according to the United Nations. About 26 million people live in Iraq.
"It's been a simmering crisis for quite a while, and it's just coming to everybody's realization," said Robert Breen, the representative in Amman for the United Nations High Commissioner for Refugees.
Further compounding the situation, Jordan and Syria recently tightened their border crossings, making it more difficult for Iraqis to escape, leaving long lines of people at the border hoping to get out. Other neighboring nations, Saudi Arabia, Kuwait, Turkey and Iran, have been even more strict about letting Iraqis in. (See where Iraqis are fleeing)