The United Nations refugee agency says one million people have fled the civil war in Syria, mostly to neighbouring countries who are struggling to support them.
More than 400,000 - nearly half the total figure - have left the country since 1 January.
Around half the refugees are children and the numbers are mounting every week.
''Thousands of people continuing to cross the border every day, Syria is spiralling towards full-scale disaster," UN High Commissioner for Refugees Antonio Guterres said in a statement on Wednesday.
An estimated 70,000 people have been killed since an uprising against President Bashar al-Assad began nearly two years ago.
Most have fled to Lebanon, Jordan, Turkey, Iraq and Egypt and some to North Africa and Europe.
Lebanon - the country closest to Damascus - has received the most refugees. One in five people in Lebanon is now Syrian.
The UNHCR said services in Jordan are being strained to the limit. Turkey has spent more than $US600 million setting up 17 refugee camps, and more are under construction.