Medecins Sans Frontiers (MSF) aid workers who were kidnapped on Wednesday were freed on Saturday evening; a Sudanese guard who was kidnapped along with them was not released.
The workers were arrested after the international criminal court issued an arrest warrant for President Omar Hassan al-Bashir on charges of orchestrating war crimes in Darfur.
MSF Belgium's general director Christopher Stokes told a news conference in Brussels MSF had paid no ransom. He said the group was reconsidering its operations at the scene of one of the world's worst humanitarian crises.
We are as a movement...not able today to determine the level at which we are able to maintain our assistance in Darfur. This includes all projects in Darfur, he added.
North Darfur governor Osman Yusuf Kibir, who accompanied the freed aid workers to Khartoum, said kidnappers calling themselves the Eagles of Bashir had freed them at an agreed site in north Darfur, Reuters reported.