At least 50 people were killed by suspected Boko Haram fighters on an island in Lake Chad on December 22.
According to local news reports, the fighters who were disguised as traders attacked fishermen on the island. The authorities confirmed that among those killed in the attack were at least 20 Cameroonians.
The identities of the victims, believed to be of mixed nationalities, were not immediately disclosed.
An unknown number of people are still missing.
Although the militia group was formed in Nigeria in 2015, the group has recently been active in Chad since Chadian soldiers stopped patrolling the area.
The Multi-National Joint Task Force formed to fight the group is inadequately equipped to patrol the Lake Chad Basin.