At least 100 jihadist fighters have been killed in an operation against Boko Haram Islamists holed up on the islands of Lake Chad, the Chadian army said in a statement.

"117 terrorists have been killed, two Chadian soldiers died and two others were wounded" in the operation against the Nigeria-based movement, which began two weeks ago, army spokesman Colonel Azem Bermendoa Agouna said, according to the Sunday Times on Friday.

"For two weeks, Boko Haram terrorists have been trying to infiltrate our islands on Lake Chad to varry out attacks on peaceful citizens," Azem said, adding that military operations were ongoing.

Lake Chad is a strategic region where the borders of Chad and northeast Nigeria converge with those of Cameroon and Niger, further north.

Boko Haram has carried out raids and suicide bombings in all four countries, which have formed a military alliance along with Benin to tackle the movement.