At least three rangers were killed by the Mai-Mai militia in the Virunga National Park in the Democratic Republic of Congo, the national park says on its website.
Charles Paluku Syaira, Jonas Paluku Malyani and Pacifique Musubao Fikirini, died in the wee hours on Monday following an attack by the militia.
The three were attacked while on patrol at the park.
One more ranger was still yet to be accounted for.
"Our thoughts and sincere condolences are with the families and widows of Rangers Charles Paluku Syaira, Jonas Paluku Malyani and Pacifique Musubao Fikirini," the report said.
At least eight rangers have been killed in the line of duty in 2017.
Less than a month ago, at least 6 rangers were found alive in a large forest reserve in DRC's northeast a day after a security station was attacked by militia.
During that attack an American journalist and at least three other security guards remained missing.
Mambasa territory administrator Alfred Bongwalanga Efoloko confirmed that the six had been found.
The park rangers are part of the Congolese Institute for Nature Conservation.