"With Virunga National Park being within our zone of action, we have joined the park rangers for search operations for the people taken hostages", Major Guillaume Kaiko Ndjike, the army's spokesman in North Kivu, said on Saturday.
The Telegraph newspaper reported that the tourists were heading to the city of Goma when the vehicle was attacked by an armed group and the two tourists, as well as the driver were abducted.
Joel Wengamulay, spokesman for the Congolese Institute for The Conservation of Nature, advised the United Nations -backed Radio Okapi that the kidnapping occurred Friday within the Nyiragongo territory simply north of Goma.
Two British citizens have been kidnapped in the Democratic Republic of Congo, sources have said.
Britain's worldwide and Commonwealth Workplace says it's in touch with Congolese authorities following an incident involving two British nationals.
A female park ranger travelling with the pair was killed, according to local media reports.More news: Consumer prices rebound 0.2% in April on jump in petrol
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More than 175 rangers have died protecting Virunga National Park, which is located in the rugged mountains and volcanic plains adjacent to neighouring Rwanda and Uganda.
Last year, a fifth of the park's southern sector was deforested owing to illegal charcoal production.
There are more species of mammals, birds and reptiles in the park than anywhere else on Earth, and almost a third of the world's 1,000-odd mountain gorillas.
On April 9, five rangers and a driver were killed in an ambush in the park, which was established in 1925.
Rising violence in recent months across the province of North Kivu has been linked to broader political instability in DR Congo. Park officials blamed Mai Mai militia members.