Chadian President Idriss Deby says about 700 people were killed in fighting sparked by a rebel attack on the capital last month.
Mr. Deby gave the updated death toll Friday during an interview with a French television station, France 24. Chad had previously placed the death toll from the fighting at 400.
Chadian rebels attacked the capital, N'Djamena, on Februrary 1 in an effort to overthrow the president. Government forces pushed the insurgents back after a three-day battle.
Mr. Deby Friday again accused Sudan of backing the rebels. He said Sudan wants to install Islamic governments throughout sub-Saharan Africa.
Sudan has denied supporting the rebels, and accuses Chad of aiding rebels in Sudan's war-torn Darfur region.
President Deby and Sudanese President Omar al-Bashir are scheduled to meet in Senegal's capital, Dakar, next week during a summit of the world's Muslim leaders.
Senegal President Abdoulaye Wade had said he will mediate talks between the two leaders in an attempt to diffuse tensions.