Updated

The U.N. is launching an investigation into attacks on peacekeepers in a part of Congo where the deadliest single assault on a U.N. peacekeeping mission in almost 25 years unfolded last month.

Secretary-General Antonio Guterres announced Friday he's appointing longtime U.N. peacekeeping official Dmitry Titov to lead a special investigation into attacks around the town of Beni.

The probe will focus on the Dec. 7 rebel attack that killed 15 peacekeepers and wounded over 40 others at a base near Beni. The dead were Tanzanian.

The attack has been blamed on the Allied Democratic Forces, one of various armed groups in the mineral-rich region.

The U.N. peacekeeping mission in Congo is the world's largest. The investigation will evaluate its preparedness and response to attacks and provide recommendations on preventing them.