Separatist Islamist rebels have released a Swiss Christian woman kidnapped by a private militia on April 15 amid political turmoil in Timbuktu, Mali, according to a Swiss foreign ministry statement.

Compass Direct News said that armed members of the militant Islamic group Ansar Dine handed Beatrice Stockly to Swiss diplomats on Tuesday, Reuters reports.

Before rebels captured Timbuktu on 1 April, most Westerners had reportedly left due to fears of being kidnapped and passed on to Al-Qaeda cells.

"The terrorist group's North African branch, Al-Qaeda in the Islamic Maghreb (AQIM), has been holding Westerners for millions of dollars in ransom payments from previous kidnappings in recent years," said the CDN story.

"Stockly, a Christian social worker in her 40s, had refused to leave Timbuktu, 439 miles northeast of the capital, when it fell to Tuareg rebels and Islamist extremists.

"She was in good health 'considering the circumstances', according to the Swiss foreign ministry statement. Ansar Dine militants took custody of Stockly after a shootout with an unidentified private militia that had seized her and wanted to sell her to AQIM."

Ansar Dine, which has imposed sharia (Islamic law) in areas under its control in the north, then handed Stockly to the Swiss government without demanding a ransom, according to Agence France-Presse. Stockly is reportedly safe in Burkina Faso.