Looting, fighting and the remoteness of displaced people have prevented aid reaching 282,000 South Sudanese displaced within the country during the last month, the United Nations said on Monday.
Humanitarian agencies have reached just over 40 percent of the 494,000 internally displaced in South Sudan since conflict broke out in the world's youngest state on Dec. 15, killing thousands, the U.N. said in its latest update.
In an effort to halt the worst violence since South Sudan's independence two years ago, government and rebel representatives are meeting in Ethiopia to negotiate a ceasefire, but there has been no clear progress. Rebel demands include that Ugandan troops deployed in South Sudan stop supporting government forces in combat.
"The response continued to grow but faced several challenges. These included people being displaced in remote areas, rapidly changing security conditions and continued looting and commandeering of humanitarian assets," the U.N.'s Office for the Coordination of Humanitarian Affairs said.
It said that more than 50 "access incidents" occurred, which means occasions when agencies planned to reach people in need but could not.
"Looting represented over 60 percent of the incidents," it said, followed by burglary, commandeering of vehicles, killing of aid workers and harassment.
At least three aid workers have been killed, 43 vehicles commandeered and 4,700 metric tonnes of food have been stolen, the U.N. said on Saturday.
The World Food Programme and Medecins Sans Frontieres are among the organisations that have reported looting of their assets.
Large numbers of people are believed to have fled into the bush from towns such as Bor, Malakal and Bentiu, where rebels and government troops are battling for control. Agencies have been unable to access them to gauge needs.
Aside from the insecurity, South Sudan is hard to traverse because it has barely any tarmac roads. When the rains come in March, many dirt roads become unpassable, forcing aid agencies to fly staff and supplies in.
On Sunday, senior members of the government and army attempted to force their way into a U.N. military base in Bor where civilians were sheltering, the U.N. said.
"The Secretary-General is particularly disturbed that United Nations staff were threatened by South Sudan military when they refused to allow armed soldiers to accompany civilians to visit the UNMISS protection site today," the U.N. said.
Journalists were taken to see Bor on Sunday after the government recaptured it from rebels.
U.N. Assistant Secretary-General for Human Rights Ivan Simonovic said on Friday the fighting had "now reached the threshold of an internal armed conflict", a status that could lead to prosecutions for war crimes where deemed appropriate. Simonovic, speaking after a four-day trip to South Sudan, said "mass atrocities" had been committed by both sides.