Norway has expressed concern the pair were not receiving a fair trial
A Norwegian and a former British soldier sentenced to death for espionage and murder of a taxi driver in DR Congo have lost their appeal.
A military tribunal in Kisangani rejected the plea and ordered them to pay $500m in damages before facing the death sentence.
Joshua French, who holds joint British-Norwegian nationality, and Tjostolv Moland were also accused of spying.
Their only remaining option is to appeal before the military high court.
French, 27, and Moland, 28, were sentenced to death by firing squad for murder by a military tribunal on 8 September.
They were also charged with espionage and arms smuggling.
'Miscarriages of justice'
The ruling drew immediate international protests.
Norway condemned the verdict and said it would complain to the government of DR Congo.
"Norway is a fundamental opponent of the death penalty, and I will as soon as possible contact the DR Congo foreign minister to relay this message, " said Foreign Minister Jonas Gahr Stoere in a statement.
The human rights group Reprieve claims the two men have suffered a series of miscarriages of justice since their arrest, reported the Press Association news agency.
"Today, in the farce that substitutes for military justice in the DRC, the judge wanted to dispense with translators," said Reprieve director Clive Stafford Smith.
"Apparently Joshua French did not have to understand the process that led to his death sentence," said the director.
"The 'legal process' has so far included torturing Joshua, parading him around town in front of lynch mobs, and forcing him to sign statements under threat of death."
"Witnesses who testified against the pair received $5,000 each in compensation in a country where people earn about $3-4 a day."
Mr Stafford Smith ended with a plea to the British government to "redouble its efforts to end this nightmare."
French was born in Norway to a British father and Norwegian mother, and lived in Margate, Kent, as a child.
He moved back to Norway when his parents divorced, but returned to the UK aged 20 and served in the British Army.
Along with Moland, he has been detained since May this year after the pair's Congolese driver was found shot dead in the north-east of the country.
Both men deny murdering Abedi Kasongo, 47, maintaining that he was shot and killed when their car was ambushed by gunmen on the road near the city of Kisangani.