Unidentified armed men ambushed the group on Friday morning north of Goma, the capital of Democratic Republic of Congo's North Kivu province, inside Virunga National Park.
The pair are thought to have been kidnapped while visiting the Virunga National Park, a gorilla sanctuary in the east of the African country, on Friday.
"This sad total once again illustrates the risks that park wardens take every day to protect wildlife and the waterside communities".
Britain's Foreign Secretary Boris Johnson on Sunday announced that the two Britons held hostage in the Democratic Republic of Congo have been released unharmed.
Boris Johnson didn't give any further details, but paid tribute to the authorities from the African country and the Congolese Institute for Nature Conservation "for their tireless help during this awful case".
Two British tourists who were kidnapped in the Democratic Republic of Congo have been freed, the United Kingdom government and Congolese park officials said Sunday.
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One of her colleagues at Virunga National Park described Ms Katumwa as "a devoted conservationist who died in the line of duty'".
He said: "We wish to extend our sincerest condolences to her family, and our thoughts are with all those affected by this incident".
It spans (3,000 square miles 7,800 kilometres) along the border with Uganda and Rwanda.
The Virunga National Park is home to between a quarter and a third of the world's highly endangered Mountain Gorilla, but it is also the hideout of a dozen militias and rebel outfits from three different countries, remnants of DRC's civil war, as well as bands of poachers and criminal gangs.
The park has experienced an increase in violence in recent months with armed groups staging a series of raids to steal resources, particularly charcoal.
Five Virunga rangers and a staff driver were killed just last month during an ambush in the central sector of the park.