REPUBLIKA.CO.ID, KHARTOUM -- Sudanese authorities believed a criminal gang is responsible for the abduction of a Swiss humanitarian worker who disappeared outside her home in Sudan's troubled Darfur region on Friday.

Authorities have intensified the search in and around the city of al-Fashir and believe the gang is looking for a ransom, North Darfur's Deputy Governor Mohamed Birama told Reuters on Monday.

"We expect that she will be found very soon," he said.

Switzerland on Sunday called for a rapid and unconditional release of the woman but did not give any other details about her.

Sudan will extend a unilateral ceasefire with rebels until the end of December, state news agency SUNA reported on Sunday, days after the United States lifted 20-year-old sanctions tied to progress on resolving ongoing conflicts.

The conflict in Darfur began in 2003 when mainly non-Arab tribes took up arms against Sudan's Arab-led government.

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