DAKAR, Senegal—A triple suicide bombing at a market on an island in Lake Chad has killed at least 27 people and injured 90 others, a Chad security official said.

Paul Manka, a Chad police spokesman, said three females carried out Saturday’s attack on Koulfoua Island.

Gen. Banyaman Cossingar, Chad gendarmerie director general, confirmed the attack, saying Nigerian Islamic extremist group Boko Haram is suspected.

The Lake Chad region, which straddles the borders of Chad, Cameroon, Niger and Nigeria, has been regularly targeted by the extremists. Chad’s government has already imposed a state of emergency in the area.

Boko Haram, the Nigerian Islamic extremist group whose six-year uprising has killed some 20,000 people, stepped up attacks this year in neighboring Chad, Niger and Cameroon after those countries agreed to help fight the insurgents.