The United Nations agency for refugees is predicting that up to 700,000 Syrians will flee their homes to other lands by the year’s end.

The UNHCR appealed Thursday with 51 other aid groups for half a billion dollars in aid to help the “rapidly increasing” numbers trying to cross the borders into neighboring countries daily.

Up to 3,000 Syrian civilians are desperately attempting to reach Jordan, Lebanon, Iraq or Turkey, said the U.N. agency. On Wednesday alone, more than 305 people died across Syria, including some 200 civilians.

Twin suicide bombings at 7:00 a.m. local time Wednesday also destroyed two buildings housing top military headquarters for the Syrian army and air force in Damascus. The attack by rebel forces mirrored a similar bombing on July 18 that killed three of President Bashar al-Assad’s closest advisers, including his brother-in-law, General Assef Shawkat, as well as Syria’s defense and interior ministers.

The number of refugees that have registered with the agency since March, and those still waiting to register, has jumped more than 600 percent, according to the U.N. statement. The British-based ‘Save the Children’ organization on Tuesday published first-person accounts from interviews with refugee children who said they had witnessed massacres and seen family members killed during the 18-month-old conflict.

More than $141 million has already been donated toward humanitarian aide for the refugees, said the aid groups in their joint appeal.

An estimated 294,000 Syrians have already fled their homeland, and “we have only one-third of the funding we need to respond,” said Panos Moumtzis, Syria coordinator for the U.N. High Commissioner for Refugees.

Turkey has already accepted some 88,000 refugees; in Jordan, 95,000 Syrians are living in tent cities along its northern border as well. Another 78,000 Syrians are now living in Lebanon, and at least 33,000 refugees have fled to Iraq, which opened a border crossing at al-Qaim.

Refugees are fleeing Syria at the rate of approximately 2,000 to 3,000 per day at present – and there seems to be no end in sight thus far in the savage civil war that so far has ended more than 27,000 lives.

“We are running out of time, warned Moumtzis, “and we need to respond.”