GOMA, Congo (AP) — Four people were killed in an ambush Thursday in Congo’s Virunga National Park when their convoy of vehicles was attacked by gunmen, according to a statement by local conservation authorities. A further six people were injured, including villagers from the Lubero Territory where the attack took place.

The convoy included technical staff for rural development projects working in the park area, according to the North Kivu branch of the Congolese Institute for the Conservation of Nature (ICCN). Three of the dead were “ecoguards” working for the conservation group.

The ICCN statement said the attack was carried out by “a group of armed men belonging to the Mai Mai,” a network of local militia groups.

Eastern Congo has been wracked by violence from a myriad of armed groups for more than a quarter-century. While much of it has been linked to the struggle for control of the region’s vast mineral wealth, other tensions have stemmed from long-standing inter-communal disputes.

The ICCN condemned the attack and said the injured were receiving care at a health facility.

Virunga Park is home to some of the world’s last mountain gorillas. However, armed groups such as the Democratic Forces for the Liberation of Rwanda, known by its French acronym FDLR, the Mai-Mai and the M23 regularly vie for control of eastern Congo’s natural resources and many park rangers have lost their lives trying to protect the area.