Friday, the tourists and a driver were ambushed en route from Kibumba to Goma after visiting Virunga National Park, where one-quarter of the world's remaining mountain gorillas reside.
Two British tourists have been released unharmed by captors in the Democratic Republic of Congo, Foreign Secretary Boris Johnson announced Sunday.
They paid tribute to the "excellent support" they had received and said they would not comment any further.
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A female ranger travelling with them was killed and their driver was also taken captive, a park spokesman said.
A pair of British hikers looking for adventure in the Democratic Republic of Congo have been freed after being kidnapped, but a 25-year-old park ranger is dead.
Park director Emmanuel de Merode said: "Ranger Baraka's life was tragically cut short in service to Virunga National Park".
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A park ranger, Rachel Makissa Baraka, was killed during the kidnapping while trying to stop the kidnappers from grabbing the tourists. She is the eighth park ranger overall killed in this year alone. The park was renamed Virunga National Park in 1969.
Soldiers and park rangers are taking part in an operation to find two United Kingdom tourists kidnapped in the Democratic Republic of the Congo.
Virunga National Park covers some 3,000 sq miles (7,800 sq km) and runs along the border with Uganda and Rwanda.
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Virunga is home to about one-quarter of the world's remaining mountain gorillas, and the work of protecting them has proven unsafe.