By Patrick J. McDonnell

BEIRUT -- The number of Syrian refugees fleeing to neighboring nations and seeking aid is rising by more than 2,000 a day and may total more than 700,000 by year's end, seven times the projection made six months ago, the United Nations said Thursday.

The U.N. refugee agency and nonprofit groups are appealing for almost $500 million to help assist the flood of Syrians escaping violence in their homeland. The appeal went out Thursday to donor nations, the private sector and individuals.

The approach of winter has added urgency to the crisis. There is a crucial need for cold-weather supplies, such as blankets, heaters, warm clothes and weather-resistant tents, the U.N. says

"Many refugees are arriving with only the clothes on their backs," Panos Moumtzis, the U.N.'s regional coordinator for Syrian refugees, said in a statement in Geneva. "They need humanitarian assistance from Day One."

About 75 percent of the Syrian refugees are women and children, according to the U.N. Providing education and health care for this vulnerable population is a priority, it says.

Currently, according to official statistics, there are about 300,000 refugees in neighboring nations who have registered with the world body or are awaiting registration. In addition, the U.N. says, there may be an additional 200,000 unregistered Syrian refugees, many living in rented homes or with families.

Escalating violence in Syria has forced aid strategists to dramatically increase their projections concerning refugees. In March, officials estimated that about 100,000 Syrians would register with the U.N. as refugees by year's end. The U.N. is now projecting that as many as 700,000 registered Syrian refugees will have fled to neighboring nations by Dec. 31.

The influx has caused deep tensions and taxed resources in Lebanon, Turkey, Iraq and Jordan. Each of the neighboring nations has opened its doors to tens of thousands of refugees, housing many in spartan tent cities. Turkey has said its capacity is approaching its declared limit of 100,000; thousands more seeking to enter there are stuck at makeshift border camps.

Inside Syria, meantime, aid workers estimate that the violence has forced more than 1 million Syrians to leave their homes. Many of the displaced have been living in schools and other makeshift facilities inside Syria; the start of the school year has forced some to find other shelter. Many are expected to join the outflow leaving the country.