BENI, Congo (AP) — The United Nations Deputy Special Representative for Congo says military offenses will be launched against rebels who killed at least 15 Tanzanian U.N. peacekeepers last week in eastern Congo.

In a memorial ceremony Monday David Gressly said those who staged the assault, which wounded 50 others, will pay for their actions. The Dec. 7 attack about 45 kilometers (28 miles) from Beni was the deadliest single attack on a U.N. peacekeeping mission in nearly 25 years.

At least five Congolese soldiers also were killed in the attack. The peacekeeping base has been repeatedly attacked by rebels from the Allied Democratic Forces group.

Tanzania's ambassador in Congo Paul Ignace Mella called on the U.N. to protect its peacekeeping soldiers. The U.N. peacekeeping mission in Congo is the largest in the world.