Armed men thought to be "Mai-Mai" fighters attacked a "convoy of technicians assigned to development projects" on Thursday morning in North Kivu province's Lubero territory, according to the Congolese Institute for the Conservation of Nature (ICCN).
"Mai-Mai" is a term used in the D RC to refer communal militias.
The ICCN said that three park rangers and one technician were killed in the attack, while six people were wounded.
Colonel Alain Kiwewa Mitela, the military administrator in Lubero territory, also said that four people were killed.
He added that the attack occurred near the village of Kivale, which lies outside the borders of Virunga National Park.
The conservation group often carries out electrical maintenance jobs around the area and is mainly tasked with protecting the nearby Virunga National Park.
Virunga has been caught in the middle of militia activity left over from civil wars fought around the turn of the century.
The ICCN warned of a resurgence of violence in February after suspected Mai Mai militants attacked a ranger position in Virunga, killing one and injuring two.
A vast expanse on the border with Uganda and Rwanda, Virunga is the oldest nature reserve in Africa and is renowned worldwide as a sanctuary for rare species, including mountain gorillas.
Militias - of which dozens are active in eastern DRC - also the use the park as a hideout.
