Chad's government is blaming Sudanese militiamen for a raid on three border villages that killed nine civilians.
Chadian officials say Thursday's attack occurred in the villages of Ade, Borota and Mutaina.
The villages are near the Chadian town of Adre, the site of a rebel attack last month.
Chad's government has repeatedly accused Sudan of supporting the attack and rebel activity along the border. Sudan has denied any involvement with the rebels.
Tensions have risen between the two nations since the Adre attack. Last month, Chad said a "state of belligerence" existed between it and Khartoum.
Some information for this report provided by Reuters and AP.