The men came under machine-gun fire from some 100 unidentified militia members while attempting to secure a key transit route, said Natasha Kofoworola Quist, a regional representative of the WWF nature conservancy.
"We owe them and their families a debt of gratitude for their courage and sacrifice," she added.
Ranger Paris Paluku, married with two children, "was always at the head of any patrol, which put him at risk and ultimately cost him his life," chief warden Emmanuel de Merode was quoted as saying.
Virunga national park, on the border with Rwanda and Uganda and known for its volcanos and mountain gorilla population, has been infiltrated by four distinct militia groups in recent weeks, according to de Merode.
Local residents were said to be fleeing the area to avoid violence in "a large-scale population displacement," he said. The park is currently closed to tourists because of the instability.
More than 150 park rangers have been killed since the east of the country became a theatre of armed conflict between various groups in 1990, according to the WWF.
Its animals have also suffered, with at least 23 of the rare gorillas being killed.
More than 10,000 people have fled from DR Congo to Rwanda and Uganda following clashes between the Congolese army and mutinous soldiers, officials said Friday.
The fighting in the jungle region has pitted mutinous ex-army troops loyal to rebel leader General Bosco Ntaganda -- known as the "Terminator" and wanted by the International Criminal Court in The Hague for war crimes -- against government forces.
Some soldiers from his group, the National Congress for the Defence of the People (CNDP), have said they have broken away and formed a new militia, the March 23 Movement (M23).
Fierce fighting continued Saturday in the province of Nord Kivu, military sources said, with a colonel saying that that the rebels appeared to have outflanked government troops.
"Yesterday the mutineers retreated from their positions near Bunagana but they have now advanced on Jomba, and we don`t understand how they appeared from that side," the colonel said.
The two towns are a few kilometres part near the border with Uganda.
The colonel said two government warplanes had attacked two places in Nord Kivu near the Rwandan border, Chanzu and the Runyonyi hill, without giving further details.
He said government troops were using heavy weapons in support in the fighting at Jomba and had asked the local population to leave "so there is no confusion between civilians and the enemy."
A local lawyer and vice-president of a civil society grouping, Omar Kavota, confirmed the raids but said the mutineers were still holding their positions.
Mutineers questioned by AFP said they belonged to M23, led by Colonel Sultani Makenga, who deserted on May 4 with several dozen men and holed up in the Rutshuru territory near the border.
The mutineers said they wanted the full implementation of a peace pact signed in 2009, when they were incorporated into the national army.
On Thursday night heavy fighting took place at Runyiony, near Bunagana, and on the edge of the Virunga National Park, where Ntaganda is believed to be located.
Ntaganda is wanted by the ICC on a war crimes charge of enlisting child soldiers but Kinshasa had refused to hand him over, saying he was needed to keep the peace pact.
But he is also now wanted by the government, which holds him responsible for the mutiny.
A military spokesman said Thursday hundreds of mutineers had come back to the army, as a deadline loomed for them to fall back into rank.
But Jason Lunene, a member of parliament for Goma, the capital of Nord Kivu, said the situation "doesn`t seem to have changed very much.
"If a fair number have surrendered, others are continuing to join the mutineers, which is not to the advantage of the population," he said.
Lunene said the homes of army officers who had defected to M23 had been searched and some weapons found. (*)
Editor: Kunto Wibisono
Copyright © ANTARA 2012
