"Two of the colleagues, along with two of their trucks, have still not been released," Rafiullah Qureshi, spokesman for the International Committee of the Red Cross in Sudan, told AFP.
He said a team of eight Sudanese ICRC staff were detained by "unknown gunmen" yesterday as they travelled between Nertiti and Zalingei in Central Darfur state.
"Six of the team members have been released," Qureshi said. "They are all fine."
The staff were returning from a mission to provide first aid training, repair hand pumps and offer other assistance, he said.
More From This Section
Rebels fighting for a decade against the government in Sudan's far-west have detained soldiers and others.
Government-linked militia and paramilitary groups are also suspected to have carried out many kidnappings, carjackings and other crimes in Darfur.
Analysts say Sudan's crisis-hit regime now has less money for militias it deployed against the insurgency, and the militias are acting outside government control.