More than three million Syrians are now registered as refugees and the desperate crisis is only getting worse, the UN's refugee agency says.
The UNHCR says Syria is now "the biggest humanitarian emergency of our era" with almost half of all Syrians forced to flee their homes.
The majority of refugees have fled to countries neighbouring Syria, with most now seeking shelter in Lebanon.
More than 190,000 have been killed in Syria's three-year civil war.
Opposition groups in Syria have been fighting forces loyal to President Bashar al-Assad since his government violently suppressed protests against his rule in March 2011.
The situation has been worsened in recent months by the formation and advance of the Islamic State group, which now controls large swathes of Syria and Iraq.