By Elias Biryabarema

KAMPALA, June 23 (Reuters) - About $352 million has been pledged to help Uganda cope with an influx of refugees fleeing conflict in South Sudan, donors said on Friday.

Uganda needs some $2 billion for its surging refugee population. The money would fund operations for the next 12 months.

About 1.3 million refugees have fled to Uganda, of whom an estimated 950,000 have come from South Sudan, displaced by the country's escalating civil war.

Most of the South Sudanese are crammed into about five camps in Uganda's northwest. One of them, Bidi Bidi is among the world's largest refugee settlements, hosting about 270,000 people.

"I don't think anyone ever anticipated that we would be dealing with one million refugees out of South Sudan alone," David Beasley, executive director of the World Food Programme, told Reuters.

Food for the refugees will run out in July without more help, Beasley said.

Fighting erupted in Africa's youngest nation in December 2013 between forces allied to President Salva Kiir and his then- deputy, Riek Machar. A peace pact in 2015 briefly halted the conflict, but it exploded into war again last July.

"The international community needs to step up and needs to give to the Ugandan people and to the refugees hosted by the Ugandan people the kind of support that is absolutely needed because the circumstances in which these sacrifices are being made are extremely, extremely challenging," U.N. Secretary General Antonio Guterres said.

(Reporting by Elias Biryabarema; Editing by George Obulutsa, Larry King) ((Email:elias.biryabarema@thomsonreuters.com; Tel. +254 20 499 1232; Reuters Messaging: elias.biryabarema.thomsonreuters.com@reuters.net))