N'DJAMENA: Five suicide bombers killed 33 people in Chad and wounded 51 more in a coordinated attack suspected to be the work of the Nigerian Islamist militant group Boko Haram, a local government official said.

Witnesses reported multiple blasts that appeared to target the market in Baga Sola, directly across Lake Chad from Nigeria, and a camp housing refugees who have fled from Boko Haram.

The group have proclaimed an emirate in northeastern Nigeria, enforcing a brutal interpretation of Islamic law, and also pushed into neighbouring countries.

Dimoya Souapebe, the sub-prefect in the town, and a hospital source both confirmed the casualty figures.

"We heard three explosions. The market is on fire right now," said one security source present in the town.

Niger, Cameroon and Chad have all suffered a spillover of violence from Boko Haram's north Nigerian strongholds.

Chad spearheaded a regional offensive earlier this year that drove the Islamist fighters from many of their bases. However, the group has fought back, launching a wave of cross-border attacks and suicide bombings.

Niger, Nigeria, Benin, Cameroon and Chad have agreed to establish an 8,700-strong multinational force to take on the militants, though its formation has been delayed.

Chadian President Idriss Deby has said the force could begin operations later this month.