He said that "my thoughts are now with the family of Virunga Park ranger Rachel Makissa Baraka who was killed during the kidnapping, and with the injured driver".
The two British nationals, whose identities have yet to be made been made pubic, were abducted on Friday at the Virunga National Park, a popular gorilla sanctuary.
At 10am on Friday, militiamen ambushed a jeep taking two Britons from a nearby city to the park.
The UK's top diplomat Boris Johnson declined to offer any further details, but paid tribute to the Congolese authorities "for their tireless help during this bad case".
Two Britons held hostage in Democratic Republic of Congo have been released, Britain's foreign minister Boris Johnson said on Sunday.
"I am delighted to announce that two British nationals who were held hostage in the Democratic Republic of Congo (DRC) have been released", Johnson said in a statement.
A park ranger who tried to protect them was shot dead by the attackers.
Park Director Emmanuel de Merode said she showed "true bravery" in her work.
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A female park ranger was killed in the attack, local media reported.
"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.
Rising violence in recent months across the province of North Kivu has been linked to broader political instability in DR Congo.
Five Virunga rangers and a staff driver were killed just last month during an ambush in the central sector of the park.
The park is home to around a quarter of the world's critically endangered mountain gorillas and other endangered species, as well as lions, elephants, hippos and rare birds.
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".
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