Gold trafficking now biggest income for militias - report

"The essential revenue for armed groups comes from gold today. Of course there are other sources like logging, but gold has become the primary source," said Enough researcher Fidel Bafilemba.

"Gold is very portable, you can put it in your pocket and it is easily smuggled across the border.

"You don't need a large quantity to make a lot of money," said an anti-fraud agent of the border agency in Goma.

Roughly £20,000 worth of gold can fit in a pocket and around £430,000 in a briefcase, estimates the Enough Project, which specialises in mapping the exploitation of conflict minerals in Congo and Sudan.

Only 23 kilos of gold were officially exported from the eastern Congo in the first half of 2012 but two to four tons were taken out illegally, said the group, taking hundreds of millions of pounds worth of the country's resources.

The gold is sold on from Uganda, Burundi and Tanzania, often by shady companies officially on UN sanctions lists but trading under other names, Enough alleged.

Gold smuggler Jacques told Enough that from there he often flies to cash-for-gold traders in Dubai with his hand luggage full of gold on Emirate Airlines.

The UN estimates that almost three tons of "fraudulently traded" Congo gold has been laundered into the legal trade from Uganda to Dubai.

On top of supplying the funds for armed groups to buy weapons and ammunition, the illegal gold trade is a source of violence in itself, as armed groups fight each other for control of mines.

M23, a rebel group that formed in April and May following the defection of high-ranking officers from the Congolese army, is trying to gain control of the Rubaya gold mine in Masisi, according to Enough.

M23 leader General Bosco Ntaganda ran an illegal mineral trade network when he was in the Congolese army, making millions of pounds each year from mines including Rubaya, it says.

The miners, 40 per cent of whom are children according to the advocacy group, work in extreme conditions, with crude equipment and no safety measures.