The African Union says a Senegalese soldier was killed Friday when unknown gunmen ambushed an AU patrol near the Sudan-Chad border.
Khartoum and Sudanese rebels are blaming each other for the attack, which targeted a group of Senegalese soldiers patrolling the Darfur region.
Ten other soldiers wounded in the attack were evacuated to a local hospital for treatment.
The assailants stole an AU vehicle, using it to flee the scene.
The incident comes just days after cross-border raids on three Chadian border villages killed nine civilians.
Chad's government has repeatedly accused Sudan of supporting rebel activity along the border. Sudan has denied any involvement with the rebels.
Tensions have risen between the two nations since Sudanese rebels attacked the Chadian town of Adre last month. After the attack, Chad said a "state of belligerence" existed between it and Khartoum.