Chad's prosecutor says 60 people including suspects from Cameroon, Nigeria and Mali have been arrested over an attack in the capital earlier this month that killed dozens of people and wounded more than 100 others.

Alghassim Khamis said Sunday new details have been uncovered concerning the June 15 attack that saw one suicide bomber blow himself up outside a police station and two others near a police academy.

He said the final death toll was 38 "including the three suicide bombers."

The attack was the first of its kind on the Chadian capital and came following threats from the Nigeria-based extremist group Boko Haram.

Chad has been a major contributor to the fight against Boko Haram, which had already attacked Chadian villages along the lake dividing the two countries.