A United Nations aid worker has been shot and wounded in eastern Chad.
Aid workers are helping refugees from violence in Darfur
A man in military fatigues shot the 37-year-old Spanish woman, a Unicef employee, in the town of Abeche and made off with her jeep, witnesses said.
The woman, who was wounded in the arm, was taken to the capital, N'Djamena, where officials said she was in a serious condition.
Aid workers are in the eastern part of Chad to assist refugees from the conflict in Sudan's Darfur region.
About a quarter of the relief personnel in eastern Chad pulled out last month over security fears following a rebel attack in the capital.
In recent months, rebels and robbers have been taking advantage of a security vacuum in the region after the army withdrew to key towns.
Aid officials said attacks on humanitarian workers were increasing as the security situation deteriorated. More than 20 vehicles belonging to relief agencies have been stolen, Reuters news agency said.
"This is the first time that an aid worker has been injured in an attack here," said Claire Bourgeois, head of UN operations in Abeche.
"We really need the authorities to ensure our security."
About 200,000 refugees have crossed the border into Chad to escape the violence in Darfur.