The attack took place on Tuesday at Kaiga Kindjiria, about 150 kilometers (95 miles) north of the capital N’Djamena, he said.
He gave no further details of the incident, neither did local officials contacted by AFP.
“The blood spilt by our soldiers will not be in vain. We will win this war against the madmen of Boko Haram,” Deby vowed.
Chad has been fighting jihadists from neighboring Nigeria for years. In official communications, the rebels are invariably called Boko Haram, even though the historic group has splintered, with the emergence of a pro-Islamic State faction.
At least 26 Chadian troops were killed last August in the Lake Chad region near the border with Cameroon.
Deby, a 37-year-old general, took power last April at the helm of a junta following the death of his father, veteran president Idriss Deby Itno, from injuries he sustained while fighting rebels in the north of the country.
