Syria's humanitarian crisis is spinning out of control as refugee numbers spike and funding to help ease the suffering has yet to materialize, Britain-based charity Oxfam said in a statement Thursday.

The group's Syria crisis response manager cautioned that the United Nations' "worst-case scenario" of more than a million refugees fleeing the country by June could be realized within weeks.

About 5,000 refugees are fleeing Syria daily to neighbouring countries, including Jordan, Lebanon and Turkey — a 36 per cent increase compared to December 2012 figures, Francis Lacasse said in a news release.

The surge was placing a "massive burden" on these countries, with the potential to "undermine stability in the region," he warned.

"The humanitarian crisis is worsening day by day, leaving agencies struggling to provide help that's desperately needed," Lacasse said.

He also said that only 20 per cent of the $1.5 billion pledged by the U.S., other Western nations and Gulf Arab countries at a donor conference last month in Kuwait has been received.

Lacasse said the money is "urgently needed now" to allow agencies to continue providing basic services like food, water and shelter to ever-growing refugee populations.

Jordanian officials said they have seen a new surge in Syrians fleeing across the border into their country in recent days, as fighting intensifies in southern Syria.

This month, Jordan recorded its highest-ever influx of refugees, with more than 50,000 new arrivals.

A government spokesman for Syrian refugee affairs, Anmar Hmoud, said Jordan is now hosting 418,529 Syrian refugees. The UN said that number could rise to half a million by the end of March.

Lebanon also houses 317,229 Syrian refugees, despite severely strained resources.

The UN says there are nearly 925,000 displaced Syrians around the region.