The figure was calculated as part of a study by the humanitarian organisation International Rescue Committee (IRC) and published in the British medical weekly, The Lancet.
The IRC provides humanitarian aid in global emergencies and relief for refugees.
According to the study, "...most deaths were from easily preventable and treatable illnesses rather than violence."
The lead-author, IRC’s Richard Brennan, said: “To save lives, improvements in security and increased humanitarian assistance are urgently needed."
The findings
The IRC conducted a nationwide survey of 19,500 households and extrapolated its findings.
An estimated 3.9 million people have died since the outbreak of the conflict in 1998 to mid-2004, when the survey was carried out.
The study approximated that more than 31,000 people were dying each month due to conflict.
It also found the national mortality rate was 2.1 deaths per 1,000 per month, which was 40 per cent higher than other countries in sub-Saharan Africa.
Casualties were significantly higher in DRC's violence-torn, resource-rich eastern province.
Slow recovery
The former Belgian colony has attempted to emerge from successive conflicts which at their height drew in a number of other nations.
But a fragile peace process in the DRC has lead to presidential and parliamentary elections scheduled for later this year.
Despite the presence of the world's largest United Nation’s peacekeeping force, violence continues in Ituri, Katanga and other parts of eastern DRC bordering Burundi, Rwanda and Uganda.