The United Nations says more than 3 million Syrians have become refugees fleeing the civil war that is devastating their country. It said 6.5 million more are displaced within Syria itself.
The number of Syrians registered as refugees in neighboring countries will top 3 million on Friday, the United Nations has said in a statement.
The UN's refugee agency UNHCR said this number did not take into account the hundreds of thousands of people who had fled Syria without registering.
It said that the violence had displaced 6.5 million people - more than half of them children - within the country itself, meaning that nearly 50 percent of Syrians had been forced to flee their homes.
"The Syrian crisis has become the biggest humanitarian emergency of our era, yet the world is failing to meet the needs of refugees and the countries hosting them," US refugee chief Antonio Guterres said in the statement.
'Huge strain on host countries'
Lebanon is the country bearing the brunt of the refugee crisis, taking in 1.14 million people since the exodus began in March 2011. Jordan is hosting 608,000 and Turkey 815,000, while hundreds of thousands more are in Iraq, Egypt and other countries.
The UN described the strain on the resources of the host countries as "enormous." Many of the refugees were living in sub-standard conditions, it said.
The agency also voiced concern that it was becoming more difficult for people to leave the country, with some being forced to pay bribes at armed checkpoints along the borders or give money to smugglers to take them to safety in Jordan.
Guterres appealed for more donations to help those affected by the conflict.
"The response to the Syrian crisis has been generous, but the bitter truth is that it falls far short of what's needed," he said.
The UNHCR says $2 billion (1.5 billion euros) are needed by the end of this year alone to provide refugees with the most urgent necessities. Donors have already contributed more than $4.1 billion in aid.
The Syrian conflict, which has its roots in initially peaceful protests against the regime of President Bashar al-Assad in early spring 2011, has become increasingly fragmented along sectarian lines as time has progressed.
More than 191,000 people were killed in the first three years of the civil war, a UN report said last week.
The United States is intending to establish an international campaign to combat militants from the jihadist group "Islamic State" (IS), who have hijacked the initial anti-government insurgency to their own ends. The UN has accused the group of committing war crimes including amputations and public executions in northern Syria, sometimes in the presence of children.
tj/ng (AFP, Reuters)