More than 4 million Syrians have fled the civil war ravaging their country to become refugees in the surrounding region - a million of them in the past 10 months alone, the United Nations said on Thursday.

"This is the biggest refugee population from a single conflict in a generation," said UN High Commissioner for Refugees Antonio Guterres. "It is a population that needs the support of the world but is instead living in dire conditions and sinking deeper into poverty."

The UN refugee agency said a surge in new refugee arrivals in Turkey had already pushed the total number of Syrian refugees in neighboring countries to over 4 million.