The American aid worker kidnapped by gunmen in Niger was a Christian missionary who had links to Youth With A Mission (YWAM), a spokesman has confirmed.
Pete Thompson told The Independent that Jeffery Woodke was abducted from his home in Abalak in western Niger at around 9pm local time on Friday.
"At the time of the abduction, two other men were killed including a local Tuareg night guard and a national guard. It is not known where he has been taken and no group has yet claimed responsibility for his abduction" Thompson said.
"His family have been informed and the US government is tracking the situation."
Woodke – who has lived in Niger since 1992 – has been working with JEMED, a local organisation linked to YWAM which helps people struggling from such issues as drought, lack of access to education, and disease.
Woodke is listed as an instructor on the website of The Redwood Coast School of Missions, a Christian mission based in the town of Arcata, about 270 miles north of San Francisco in California.
"Jeff has spent over a quarter of a century involved in missions ministry," a biographical thumbnail of Woodke on the Redwood Coast website said.
"He has committed the past 25 years of his life to a ministry he founded in Niger amongst a number of unreached people groups."
A statement from Niger's interior ministry on Saturday said after being abducted, Woodke was driven across the desert towards Mali.
"These criminals are now heading towards Mali. Our forces are on their trail," said interior minister Mohamed Bazoum.
Residents reported hearing gunfire near the aid worker's house late on Friday. The town mayor, Ahmed Dilo, told Reuters that gunmen first came on a motorbike to kill the guard before the truck came to take Woodke away.
The interior minister said one national guard stationed at the house was also killed.
Kidnappings of foreigners in Niger are rarer than in neighbouring Mali, where Islamist militants are active and often seize hostages for ransom or political capital.
The militants and allied criminal gangs have long exploited the largely unpoliced Sahara and attacks have increased this year as security worsens in Mali.
No US citizen has been kidnapped in Niger before, although in 2009 suspected Islamists attempted to abduct US embassy personnel from a hotel in the town of Tahoua.
A US embassy spokeswoman said there was an investigation into the incident but could not confirm any additional details. The US State Department said it was aware of reports but declined to comment citing US privacy laws.
Additional reporting by Reuters.