Chadian army officials report military forces have killed about 1,000 Boko Haram extremists in an operation on the islands of Lake Chad.

In a video statement released late Thursday, Army spokesman Colonel Azem Bermandoa said the eight-day operation cleared the extremists from the islands in a vast area between Chad, Nigeria, Niger and Cameroon.

He said 52 Chadian army soldiers also were killed and nearly 200 others wounded during the operation.

The move follows a Boko Haram attack last month on a Bohoma army base. More than 92 soldiers were killed. Army officials called it the deadliest attack ever on the nation’s forces.

Boko Haram extremists have killed tens of thousands and forced millions from their homes during their more than decade-long insurgency.