Niger's defense ministry says suspected Boko Haram fighters attacked an army base on the island of Karamga in Lake Chad.

A ministry statement read Saturday night on state television did not provide casualty figures. A military source in the region, speaking on condition of anonymity because he is not authorized to speak to the press, said the army may have suffered "heavy losses."

The statement said the assailants approached the base in about 10 motorized canoes. It said operations are ongoing "with the help of allies" to defeat Boko Haram.

Niger joined a regional offensive in January that has been credited with retaking large swaths of territory from the Nigeria-based militant group. A February attack on Karamga killed seven Niger soldiers, and Niger towns bordering Nigeria have also been targeted.