The report found that 23 African countries were involved in one form of conflict or another between 1990 and 2005, affecting long-term development.
Average annual economic loss, as percentage of predicted GDP (periods of conflict in brackets):
Burundi (1993-2005): 37%
Rwanda (1990-2001): 32%
DR Congo (1996-2005): 29%
Eritrea (1998-2000): 11%
Republic of Congo (1997-1999): 7.1%
Read the joint report here
"If [the money were] not lost due to armed conflict, it could solve the problems of HIV and Aids in Africa, or it could address Africa's needs in education, clean water and sanitation, and prevent tuberculosis and malaria," the report said.
"On average, armed conflict shrinks an African nation's economy by 15 per cent, and this is probably a conservative estimate," it said, adding that its assessment covered only the cost of armed conflict, not armed crime.
Irungu Houghton, Oxfam's African policy adviser, said armed conflict is one of the greatest threats to Africa's development.
"The costs are shocking. Our figures are almost certainly an under-estimate, but they show conflicts are costing African economies an average of $18bn a year.
"This money could solve the HIV/Aids crisis, prevent TB and malaria, or provide clean water, sanitation and education," he said.
In one example, the report said the 1998 to 1999 conflict in Guinea-Bissau had caused a negative gross domestic product growth rate of 10.15 per cent in the country.
The Guinea-Bissau economy had been projected to rise by 5.24 per cent if no civil conflict had taken place.
Joseph Dube, the Africa co-ordinator for IANSA, said the report "describes some of the devastating economic impacts of the poorly regulated international arms trade and the shocking level of human suffering that this causes".
"As an African, I implore all African governments and weapons-producing governments to support a strong and effective arms trade treaty," he said.
The report said Kalashnikov rifles were the most commonly used weapon in African conflicts, even though 95 per cent of them were made outside Africa.
In many cases, armed organisations seized such weapons from police and army stockpiles, the report said, adding that inadequate government controls over armed non-state forces had eased the flow of weapons to the illicit arms trade.
Dube called for global co-operation to curb arms trading, saying that "the government whose factory produces the rifle is as responsible as the government who permits its ships to transport them".
In a foreword to the report, Ellen Johnson Sirleaf, Liberia's president, urged Africa and the world to work towards an arms trade treaty.
|Sirleaf said a treaty should be reached to |
restrict the flow of illicit arms [GALLO/GETTY]
"At this critical time for reaching agreement on tough international controls on the arms trade ... it is essential that all governments understand the economic costs of armed violence and the impact that cost has had on development," said Sirleaf, whose country experienced 14 years of conflict until 2003.
"This is money Africa can ill afford to lose. The sums are appalling," she said.
The report said a comprehensive arms treaty should prohibit arms transfers that are likely to result in breaches of international rights laws and harm development.
However, it said any arms treaty should not undermine "the responsible transfer of weapons for defence, policing, peacekeeping, and other legitimate purposes".
The organisations which authored the report said the economic assessment is an underestimate because it does not take into account the economic impact on neighbouring countries which deal with refugees and regional instability.