NAIROBI, Kenya - Tens of thousands of refugees fleeing war in Sudan are struggling to find enough water to drink and cook with, leading to the deaths of an unknown number from dehydration and diarrhea, aid officials said Monday.

More than 35,000 people have fled Sudan's Blue Nile state for South Sudan over the last month. The refugees said they fled bombing and ground fighting between Sudan's military and a rebel group historically associated with South Sudan, the SPLM-N, the U.N. said Monday.

Thousands of the new arrivals were forced to walk about 25 kilometres (13 miles) over the last week because there wasn't enough water at their original location, said Tara Newell, an emergency co-ordinator with the aid group Doctors Without Borders.

"We did see a handful of deaths from that walk from sheer dehydration and exhaustion," Newell said by satellite phone from the Jamam refugee camp in South Sudan's Upper Nile state.

Newell said it was impossible to quantify the number of deaths, but that her aid team saw firsthand the death of a toddler.

"We arrived just as the child was dying and we were unable to reanimate the child," she said. "Witnessing a child die of dehydration is sad. Dying from a tropical disease is sad, but dying of a lack of water is just outrageous."

Peter Struijf, an aid worker from Oxfam at the Jamam camp, said that the latest influx of refugees began after shelling and bombing in the Blue Nile region of Sudan in May. He said most people had to walk two to three weeks to reach the border with South Sudan.

The majority of the new arrivals are women, the elderly and children, an indication that men stayed behind to participate in the fighting or to tend to the fields, he said.

Some 20,000 people are at a holding camp now but the camp will run out of water in a week, Struijf said.

The new arrivals said that up to 40,000 more people could be en route to South Sudan, UNHCR said.

The rainy season is about to begin in this part of South Sudan, but that will bring additional challenges. Aid workers say they would welcome the additional water, and the chance for reservoirs to refill, but it will make relocating people or bringing in food and medical supplies by the rough dirt roads much more difficult.

"We are certainly not praying for water, which is fairly unusual in Africa. We are praying for another week of dry weather so we can get everyone out," Struijf said.

A UNHCR report released Monday said that more people became refugees in 2011 than at any time since 2000. UNHCR said 2011 was a record year for forced displacements caused principally by crises in Ivory Coast, Libya, Somalia and Sudan.

The Jamam refugees are fleeing from Blue Nile State, while another refugee camp in South Sudan — Yida — has seen nearly 50,000 refugees fleeing fighting in Sudan's Southern Kordofan state.

Both internal conflicts between Sudan and the SPLM-N developed after South Sudan peacefully broke away from Sudan last July after an overwhelming vote that was guaranteed in a 2005 peace agreement. The agreement ended more than two decades of civil war between Sudan and the new state of South Sudan.

Struijf said he believes aid workers should be able to handle the situation around the Jamam-area refugee camps, but that if rains arrive early a crisis will develop, particularly because the 20,000 people in the low-water situation won't be able to move. The rainy season can last for six months in South Sudan.

"We are still playing a game of poker with the weather. But we seem to have a slightly better hand of cards now than we had two to three weeks ago," he said. He credited hard work from drilling wells to planning logistics.

Newell said that water remains an urgent priority. "It's very sad that with this number of refugees that simply having something to drink is our biggest challenge."

News from © The Associated Press, 2012