By Stephanie Holmes
BBC News website
Aid agencies say they will not cease operations in Darfur, despite spiralling security risks in the area.
Almost three million people are in need of food aid in Darfur
The Sudanese government's suggestion that the African Union withdraw and its refusal to accept UN peacekeepers has triggered fears of a security vacuum.
But humanitarian groups have pledged to stay in the troubled western region as long as they are safely able to do so.
Dozens of aid organisations are providing food, sanitation and health services to those forced to flee.
Neutrality and impartiality
"The last few months and weeks have been some of the most difficult for aid workers in Darfur," explained Greg Barrow of the World Food Programme (WFP), the UN agency feeding some 2.75 million people in the region.
More than two million people are living in camps after fleeing three years of fighting between government-backed militia and rebel groups in the region.
A total of 12 aid workers have been killed in Darfur since May alone, and aid convoys have been targeted in recent months.
The International Rescue Committee said last month that a spike in the number of sexual assaults around Darfur's largest displaced camp was "yet another sign of the region's plummeting security situation."
The situation is so tense that some humanitarian organisations declined to comment for fear of putting their local staff at risk.
But most say they will not consider pulling out unless their workers feel threatened or are directly targeted.
Humanitarian agencies have traditionally relied on the principles of neutrality and impartiality.
They believe that if all the parties to a conflict understand their aims they can continue to operate, without being drawn into the conflict themselves.
Mr Barrow said that the sheer levels of banditry and armed attacks make it difficult to distinguish criminal acts from politically motivated ones.
"It is a lawless part of the world where many people are armed," he said.
Marco Jimenez, of the International Committee of the Red Cross (ICRC), which has about 1,800 staff in the region, said communication was vital.
"The key method we use in Sudan, as elsewhere, is we notify all parties to the conflict of our every move and every activity," he said.
But the complicated and fragmenting nature of the conflict in Darfur, as rebel groups split and loyalties change, is challenging this ideal.
"The problem with the increasing division in the rebel groups is that we no longer know who are interlocutors are, in order to be able to keep the commanders informed," he said.
BBC Africa analyst Martin Plaut says the unexpected announcement by Khartoum that it wants the AU troops to leave by the end of the month may indicate it is planning a military showdown against rebel groups in the region.
But aid agencies say they will continue to be resilient and respond to need.
"There has been a deteriorating security situation for the last two months now," said Mr Jimenez.
"The departure of the African Union troops may have a negative impact but, to be honest, it cannot get much worse."