Boris Johnson did not supply any additional particulars within the assertion launched Sunday, however paid tribute to the authorities from the African nation and the Congolese Institute for Nature Conservation "for his or her tireless assist throughout this awful case".
A park ranger who tried to protect them was shot dead by the attackers.
The park's director, Emmanuel de Merode, said: "Ranger Baraka's life was tragically cut short in service to Virunga National Park".
Security guard Katumwa, 25, was killed defending the British pair, becoming the first female ranger in the history of the park to be murdered by bandits.
"We wish to extend our sincerest condolences to her family, and our thoughts are with all those affected by this incident".
The Foreign Office had been in contact with local authorities since the event took place.
The Britons were among a group of people taken hostage, according to a spokesperson for the Congolese Institute for Nature Conservation (ICCN). Park officials blamed Mai Mai militia members.
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It spans (3,000 square miles 7,800 kilometres) along the border with Uganda and Rwanda.
Last month, five young rangers and a driver in the park were killed in an ambush.
The Foreign Office now - and before the kidnapping - advises against travelling to the area.
Virunga is home to about a quarter of the world's remaining mountain gorillas, and the work of protecting them has proven unsafe.
The advice, last updated four days ago, says tourists are vulnerable if travelling without escorted transport in the eastern part of the country, and the "risk of kidnap or injury as a result of armed or criminal activity remains high".
Earlier in May, British NGO Global Witness published documents it said showed the Congolese government's plan to "declassify" over 20 percent of the area of the park to explore for oil.