Five rangers and their driver have been killed at the Virunga National Park in the Democratic Republic of Congo, a spokesman says.
The group was killed in an ambush by suspected rebels operating in the park, Joel Wengamulay told the BBC.
Virunga boasts Africa's most diverse wildlife habitat and is home to endangered mountain gorillas.
Some of eastern DR Congo's armed groups are also based in the park, where they often poach animals.
Virunga is home to about a quarter of the world's remaining 880 mountain gorillas, as well as lions, elephants and hippos.
More than 130 park rangers have been killed in the park since 1996.
Eastern DR Congo is a mostly lawless region, hit by conflict between the government and various armed groups.