The Medecins Sans Frontieres staff - a French administrator, a Canadian nurse and an Italian doctor - were safely back in the Sudanese capital Khartoum.

One of two Sudanese MSF employees seized at the same time was later freed. The other, watchman Sharif Mohamadin, was released at the same time as the three foreigners.

MSF had run the only health clinic for the Saraf Umra area's 60,000 residents.

The clinic is run by MSF's Belgian branch, which is not among more than a dozen aid groups expelled from Sudan after an international indictment was issued this month against President Omar al-Bashir for alleged war crimes in Darfur.

Khartoum has accused the groups of spying - a charge they strongly deny.

The Sudanese authorities initially said the gang responsible for the latest abductions were bandits seeking a cash ransom.

Both the local Sudanese governor and Italian Foreign Minister Franco Frattini insisted no ransom had been paid to secure the release of the hostages.