Sudanese authorities have freed a Swiss humanitarian worker who was abducted in the war-torn southern region of Darfur last month, the deputy governor of North Darfur, Mohamed Barima, told Reuters on Wednesday.

Sudanese authorities previously said they believed a criminal gang had abducted the Swiss woman outside her home near the city of al-Fashir and the Swiss government has called for her immediate release.

Barima said the woman was in good health and being held at a security headquarters in the southern town of Kutum in North Darfur.

The Swiss and Sudanese governments have not identified the woman.

A spokesman for the North Darfur government said security forces launched an operation early on Wednesday morning to free the woman from where she was being held in a rural area just outside Kutum.

Sudanese officials did not name a group responsible for the kidnapping or provide further details of the rescue operation.

Khartoum has been at war with rebel groups in Darfur since 2003, when mainly non-Arab tribes took up arms against Sudan's Arab-led government.

Sudan has been keen to show it is making progress in winding down long-standing conflicts after the United States lifted 20-year old sanctions last month. Just after the sanctions decision Khartoum announced it would extend a unilateral ceasefire with rebels until the end of December.