Three wildlife wardens and a member of the armed forces were killed as they attempted to tackle elephant poachers in the Democratic Republic of Congo's Garamba national reserve, an African conservationist group which manages the park said.

"The incident occurred when the men, all members of a 10-man Garamba patrol team, tracked the collar of a poached elephant to a poachers' camp," the African Parks group said in a statement.

An exchange of fire ensued "during which the outnumbered Garamba unit was forced to disperse" and the three wardens and a member of the Congolese Armed Forces (FARDC), who was assisting with patrols, were killed, it added.

An African Parks helicopter that was sent out to rescue the rangers itself came under fire but managed to retrieve six members of the patrol unit and drop them at a safe area, but was unable to return for the others.

The four bodies were recovered on Thursday when a reinforced patrol team managed to access the site of the incident, said African parks which manages the reserve alongside the Congolese Institute for Conservation and Nature (ICCN).

The deaths bring to eight the number of people killed in the Garamba park this year.

"The big herds for which the park is famous makes it an ongoing target for well-organised, well-armed and well-equipped poaching groups," African Parks said in its statement, sending its condolences to the families of those killed.

Garamba National Park, in the far northeast of DR Congo, is classified as a World Heritage Site by UNESCO.

It is also home to the last surviving population of wild northern white rhinos.

The national park is situated in an unstable region bordering South Sudan and near Uganda, where Uganda's brutal Lord's Resistance Army rebels operate.