(CNN) -- An American citizen is among three aid workers kidnapped in the war-torn western Sudanese region of Darfur, the U.S. Embassy in Khartoum said Wednesday.
The 36-year-old Californian woman was with two Sudanese colleagues when their two-vehicle convoy was stopped by a group of armed men Tuesday, said Samaritan's Purse -- the organization for which they work.
The abduction took place about 25 miles southwest of Nyala, the capital of South Darfur state.
The North Carolina-based organization said it was working with U.S. and Sudanese government officials to secure their release.
The U.S. Embassy also is monitoring the situation, said spokeswoman Judith Razen.
Samaritans's Purse, founded by evangelist Franklin Graham, said it has provided $83.7 million in assistance to Sudan since 2001.
Darfur has been beset by conflict since 2003 after rebels began an uprising against the Sudanese government.
To counter the rebels, Arab militias with ties to the Sudanese government went from village to village in Darfur, killing, torturing and raping residents there, according to the United Nations, Western governments and human rights organizations. The militias targeted civilian members of tribes from which the rebels drew strength.
The United Nations estimates that 300,000 people have been killed in the conflict in Darfur, and 2.5 million have been forced to flee their homes. Sudan denies the death toll is that high.
The International Criminal Court has issued an arrest warrant for Sudanese President Omar Hassan al-Bashir, accusing him of war crimes and crimes against humanity -- charges he denies