Two Moroccan U.N. peacekeepers in Central African Republic were killed and two others wounded by unknown attackers in the southeast of the country, the U.N. mission there said on Wednesday.

The peacekeepers were escorting fuel trucks on Tuesday afternoon about 60 kilometres (37 miles) west of the town of Obo when they were attacked, the mission said in a statement, adding that the assailants fled into the bush.

“No claim can justify individuals directing their grievances against peacekeepers whose presence on CAR soil is only aimed at helping the country emerge from the cycle of violence,” mission head Parfait Onanga-Anyanga said in the statement.

Central African Republic descended into chaos in 2013 when mainly Muslim Seleka rebels seized power in the majority Christian nation, ousting then-President Francois Bozize and sparking a backlash from Christian militias.

The U.N. mission has 13,000 peacekeepers on the ground, but some civilians complain that it does not do enough to protect them against dozens of armed groups.

Last month, U.N. sanctions monitors said that violence was spreading despite successful polls that elected a new government last February. Human Rights Watch said a new armed group had killed at least 50 civilians in a growing campaign to control parts of the northwest.