The aid agency Concern has announced that it is to withdraw all non-essential staff from the Darfur region of Sudan.
The decision follows a series of attacks on aid workers and humanitarian vehicles in the troubled region.
Last week, the aid agency Goal said that it was withdrawing its remaining international staff from Darfur.
Concern says that it is leaving one essential programme manager in Darfur.
The organisation says it intends to move back into the region as soon as possible depending on the security situation.
Oxfam International, the International Rescue Committee, Norwegian Refugee Council and World Vision have all withdrawn staff temporarily because of the attacks on aid workers and their vehicles.
EU and US step up pressure on Khartoum
The European Union and the United States have stepped up calls for Sudan to let international troops in to support African Union forces in Darfur amid growing talk of sanctions on Khartoum.
The calls followed warnings from London and Washington that Sudan could face measures such as imposition of a no-fly zone over its vast west if it did not agree to such a force soon.
'Time is of the essence in a dire humanitarian situation,' EU leaders said in a joint communique issued after talks on Darfur at a European summit in Brussels.
'(The EU) strongly urges the government of Sudan to give its unequivocal consent to the implementation of the UN support package for the AU mission in Sudan in its entirety.'
The UN support package is due to gradually turn the AU mission into a hybrid UN-AU operation.
Sudan has so far refused to allow an international force to go to Darfur to end three years of fighting that has killed over 200,000 people.
