Five Chadian security officials and six militants have been killed in an explosion during a raid on a weapons cache in the capital N'Djamena, officials say.
Officers seized weapons and explosives at the scene, the state prosecutor told Reuters news agency.
Militants refused to surrender and then blew themselves up when police arrived at the building, local media report.
At least 33 people were killed last month in a bomb attack in N'Djamena.
The government has blamed the Nigerian Islamist militant group Boko Haram for the June attack, but the group not yet commented.
It had previously threatened to attack Chad, after it sent troops to help Nigeria recapture territory from the militant group.
Authorities in Chad arrested 60 suspected militants on Sunday, saying they had dismantled the cell responsible for the deadly attack in June.
The "mastermind" of Boko Haram activities in Chad and northern Cameroon was also arrested as part of Sunday's operation, the country's interior minster Abderahim Bireme Hamid said.
One of those arrested on Sunday gave up the location of a safe house in the capital where militants were making bombs and storing weapons, which resulted in Monday's deadly police raid, he added.