Boko Haram militants carried out an attack on a military post in Chad’s Lake Chad region late Monday night, Chad’s armed forces said Tuesday, killing 23 soldiers. Chad also said the attack left 26 other soldiers injured and that the militants were eventually driven back.

Chad’s military described the assault as taking place on Barka Tolorom island and said it was repelled after fighting broke out. In a statement, the armed forces said “a significant number of sect members were neutralized,” adding that the attackers were pushed away.

President Mahamat Idriss Déby responded to the attack in a separate statement, describing it as “cowardly.” The president’s comment came as the country continued to report details about the casualties and the outcome of the fighting at the post.

The Lake Chad region has long been threatened by Boko Haram, a Nigeria-based militant group known for attacking in neighboring countries. The wider area, spanning four countries, has also been shaped by competition among armed groups that seek funds by imposing what they call taxes on local communities.

Over the past decade and a half, the United Nations has said Boko Haram has killed several thousand people and displaced millions, and has continued operations across parts of Nigeria, Cameroon, Chad and Niger.