The Chadian government declared three days of national mourning Monday following the killing of dozens of soldiers in Lac province.
In a decree, the government said that from Tuesday midnight to Friday, flags will be flown at half-mast and all festive activities will be prohibited throughout the country.
Only religious music and prayers will be allowed in the media and places of worship, it said.
A deadly attack on a military base in Lac province left at least 40 soldiers dead, according to the president's office.
Sunday's attack by unidentified assailants targeted a Defense and Security Forces base in Barkaram, an island in Chad's Lake region.
President Mahamat Idriss Deby Itno vowed to hunt down the assailants, who he said plunged many families into mourning.
"Wherever they go, one by one...they will see in a few days the lightning of the Chadian National Army," Deby said.
Chad has been battling an insurgency in the Lake Chad region, where government forces regularly clash with militant groups, including Boko Haram.
