Joshua French (left) and Tjostolf Moland (right) stand in court at their appeal in 2010 - Heiko Junge Scanpix
"He's been my best friend, and I will never get such a good friend again," he told Dagbladet newspaper from the yard of his prison in Kinshasa. "I do not think it is possible to know anyone better than we did."
The 31-year-old, who has joint British and Norwegian citizenship, has been moved to a large shared cell with ten other prisoners since finding Moland dead in the cell they shared on Sunday.
"I have not had time to mourn, for I have not been alone for one minute," he told the paper. "They dare not leave me alone."
The two soldiers, who were in the Democratic Republic of Congo to set themselves up as security contractors, were found guilty in September 2009 of murdering their driver Abedi Kasongo.
French said that Africa had brought out the best in his friend.
"I have so many good things to say about Tjostolf. Africa was definitely his element. He was an adventurer, a tough guy, and a very intelligent guy."
French said he feared that he would now be blamed for the death.
"Of course I'm under investigation," he said. "There were two men locked in a cell and is now one is dead. It's quite natural."
Experts from Kripos, Norway's specialist criminal investigation service, are flying to Kinshasa to witness the autopsy of Moland's body.
Major Flory Kadimba, a senior officer at the prison, on Wednesday told VG that Moland had been in good shape just the day before he died.
"He was out running in the yard the day before. He was fine, and no indication that there was anything wrong," he said.
Meanwhile diplomats are negotiating both to be able to take the body home to be buried, and to secure French's transfer back to Norway.
"Our highest priority, after the tragedy that happened to Moland, is to get French home," Foreign Minister Espen Barth Eide told VG. "Whether in the form of a prison transfer or a pardon, and preferably the latter."
A letter sent by Prime Minister Jens Stoltenberg to Congo's President Joseph Kabila in February 2012 requesting his "prompt assistance…to bring to an end this deplorable affair" has yet to be answered 18 months later.