Gunmen in Sudan's troubled Darfur region were holding two employees of the Red Cross on Tuesday but six others have been freed, a spokesman for the organisation said.
"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" on Monday 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.
Qureshi said the release came after contacts with "various levels of political, military, intelligence and tribal authorities that have influence in the area."
In addition to aid work the ICRC, as a neutral intermediary, has facilitated the handover and repatriation of numerous prisoners held by groups in Darfur.
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.
Elsewhere in Darfur, a helicopter and its crew contracted by peacekeepers have been detained by rebels of the Minni Minnawi faction since early August.
"UNAMID was informed that negotiations have been initiated for the safe release of the crew," an official of the African Union-UN Mission in Darfur told AFP on Tuesday.
UNAMID says the Mi-8 chopper was contracted by a Russian company and did not carry UN markings when a mechanical failure forced it to land southeast of Nyala city, leading to the capture.
In an unrelated incident, UNAMID said a search continued on Tuesday for four peacekeepers swept away on Sunday by a flash flood while they escorted an aid mission in West Darfur.
Rescuers found two other peacekeepers alive.