Officials from a United Nations food agency air-dropped 32 metric tons of food to refugees on the South Sudan-Sudan border, an expensive, last-ditch way to get food to tens of thousands of people who have been forced out of Sudan by fighting and hunger, an official said Thursday.

The food was wrapped in rugged bags and pushed out of a cargo plane that flew low and slow, then pointed its nose upward so the cargo slid out the rear, said Challiss McDonough, a World Food Program spokeswoman. No parachutes were used. The air drop was used because a long rainy season has created muddy conditions, making ground deliveries slow and difficult for the refugees who have trekked to the camps.

"This is the first in a series of airdrops that aims to replenish rapidly diminishing food stocks for more than 100,000 people who have fled the fighting north of the border," said WFP Director Ertharin Cousin, who is touring the region.

The first airdrops were made Wednesday in Maban County in Upper Nile state. Camps there — along with another in the region called Yida — have received more than 160,000 refugees who have fled war on the other side of the border in Sudan.

The refugees in Maban come from the Nuba mountains in Sudan's Blue Nile state. They have fled fighting between the rebel SPLM-North and Sudanese government forces. Fighting between the government and the rebels broke out in Sudan's South Kordofan State following South Sudan's independence in July 2011. The clashes spread to neighboring Blue Nile state.

Since then, refugees have been pouring across the border. In camps along the north-south border, refugees have endured food and water shortages as well as the occasional bombing, which South Sudan says are carried out by Sudanese warplanes.

An American living in the Nuba mountains, Ryan Boyette, said Thursday that Antonov airplanes have dropped several bombs on multiple villages in the region over the last week.

WFP plans to deliver up to 2,000 metric tons of food to Maban over the coming days and weeks. The food is being flown from Gambella, in neighboring Ethiopia.

The camps in Upper Nile sit in one of the most remote and underdeveloped regions in South Sudan. During most of the year, food is brought in over unpaved roads or flown in on planes and helicopters. But with the start of the rainy season in June, roads and runways have deteriorated, making transport difficult.

WFP resorted to the food drops because of a greater influx of refugees than had been expected.

"WFP had prepositioned food stocks earlier in the year, but we had about 35,000 extra refugees come in so now we have to replenish the stocks," said George Fominyen, a WFP spokesman.

The seasonal rains have created dangerous health conditions for the refugees. According to Doctors Without Borders, also known by their French initials MSF, a quarter of children in Maban's Batil refugee camp are malnourished. MSF says more than two children out of every 10,000 are dying each day in the camps.

"The rainy season has turned these camps into nightmare places to be a refugee," says Bart Janssens, MSF operations director.

Across the border in South Kordofan, Boyette, a former American aid worker who now lives in the region and helps run a news website there, said Thursday that he heard bombings by Antonov planes on Tuesday, and that he later confirmed that seven bombs were dropped in two different villages. He said an Anotonov plane on Sunday bombed two other villages.

The bombings took place despite an agreement earlier this year that was to enable observers from the African Union, League of Arab States and U.N. to help aid groups gain access to the region to deliver humanitarian supplies, Boyette said. Boyette said he believes the bombings are part of an attempt by Sudan to discourage the assessment team from visiting the region.


Associated Press reporter Jason Straziuso in Nairobi, Kenya contributed to this report.