The UN is hiking its estimates of people trapped in Syria after fleeing their homes, saying Wednesday some four million are now displaced inside the country and in dire need of international help.
The figure, due to be officially released in the coming days, is a dramatic increase on earlier estimates of some 2.5 million displaced put forward by the UN High Commissioner for Refugees for the period from January to June.
It also adds to the 1.2 million refugees who have fled to neighboring countries -- meaning that almost a quarter of the nation's population of around 22.5 million has now been forced to flee the two-year conflict.
UNHCR regional public information officer Reem Alsalem acknowledged the initial figures laid out in the Syria humanitarian assistance plan earlier this year "no longer reflect the quickly evolving situation."
"The UN and its partners are currently in the process of revising the planning figures, scenarios and response mechanisms from now until the end of the year," she told AFP in an email.
Of the number of internally displaced people inside the Syria "it would be safe to say that they are around four million," she added.
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Aid workers have struggled to reach those in most need, braving dangerous situations to get shelter, food and help to those fleeing the fighting.
But the crisis is also stretching resources as the United Nations, aid agencies and donors -- the biggest of which so far is the United States -- scramble to keep up with the flow of frightened families.
Health services, bakeries, schools, vital components of normal life are teetering or have shut down, leaving a population in distress.
"What we're seeing now... is that now it is not just violence that is driving flight," Deputy Assistant Secretary for Population, Refugees and Migration Kelly Clements said.
"It is also just a decline in livelihoods, a decline in the economic means for families to be able to support themselves, it's disruption to services, it's kids not being able to go to school, it's water systems that have been either cut off or somehow affected."
The United States has so far provided some $385 million for humanitarian aid, of which nearly $216 million has been spent on needs inside Syria, working through agencies such as the UNHCR and the World Food Program.
Donors who gathered at a conference in Kuwait in January pledged some $1.5 billion in aid for the Syrian people -- of which $520 million was specifically to help people trapped inside the country.
But to date only about 30 percent of the funds pledged have actually been received.