Armed men ambushed and killed seven U.N. peacekeepers trying to protect villagers in Ivory Coast on Friday and more than 40 of their colleagues who stayed to guard from more attacks remain in danger, the United Nations said.

Hundreds of villagers were fleeing the area near the Liberian border, and U.N. officials said others may have been killed or injured. Authorities have been unable to confirm any additional casualties because of the remoteness of the area near the Liberian border.

U.N. Secretary-General Ban Ki-moon condemned the attack "in the strongest possible terms," saying he was "saddened and outraged" about the deaths of the peacekeepers, all from Niger. He urged the government of Ivory Coast to identify the perpetrators and bring them to justice.

Ivory Coast's deputy defense minister Paul Koffi Koffi said government forces, along with Liberian and U.N. forces, will launch an operation on June 15 to find the men responsible. He said they were "militia men or mercenaries."