The Chadian army says it engaged in heavy fighting with rebels Tuesday near the country's eastern border with Sudan.
Military officials say the army moved against the rebel Assembly of Forces for Change in the hilly Kapka region.
The officials say fighting is taking place in dry riverbeds and other rugged terrain. They say the rebels have taken refuge in caves.
Chadian troops have clashed with insurgents several times over the past week since the collapse of a month-old cease-fire between the government and four rebel groups.
The main rebel group, the Union of Forces for Democracy and Development, has accused French troops in Chad of assisting the government. The group says it will fight the French army or any other foreign troops who enter Chad.
The European Union plans to send more than 3,000 peacekeepers to eastern Chad early next year. The mission is meant to protect aid operations for about 400,000 civilians displaced by violence in Chad and Sudan's neighboring Darfur region.
Some information for this report was provided by AFP and Reuters.