A French aid worker has been shot dead by unidentified gunmen in eastern Chad, an aid group has said.
Britain's Save the Children said their employee Pascal Marlinge, 49, was killed as he travelled in a convoy of vehicles near the Sudanese border.
French Foreign Minister Bernard Kouchner condemned the attack as a "barbaric act", and demanded a full investigation from Chad's officials.
The charity said the killing meant it would suspend work in the country.
A group of armed men stopped and attacked the three-vehicle convoy Mr Marlinge was travelling in at about 1000 local time (1000 GMT).
The Save the Children driver and three employees of another aid agency, whose nationalities have yet to be confirmed, are thought to have escaped injury.
Save the Children spokesman Dominic Nutt said: "We have had to shut down our vital humanitarian work with refugees who desperately need health care and feeding, and that is, of course, deeply worrying.
"Our priority is to discover how safe our staff on the ground are, and how soon we can return to normal operations in Chad."
Wife and daughters
Aid agencies have said attacks in eastern Chad have increased as fighting in Sudan's neighbouring Darfur region crosses the border.
Save the Children UK chief executive Jasmine Whitbread said: "Staff in the UK and in Chad are profoundly shocked and upset. Pascal was loved and respected by all colleagues who have worked with him."
Mr Marlinge worked in eastern Chad with displaced people and refugees as Save the Children's head of operations in the country.
His wife and two daughters have been informed of his death.