Global Witness's Charmaine Guise: "Funding the conflict"

In a new report, the Global Witness group says trade is continuing despite United Nations sanctions imposed on Unita earlier this year because of its failure to implement peace accords.

The report estimates that since 1992 Unita has earned more than $3.5bn from the sale of diamonds, helping it to re-arm itself.

Researcher Charmaine Guise, who helped compile the report, said: "Unita have been relying on diamond revenue through this whole decade to not just fund their war but also to help them to undermine the peace process."

Routes altered

In June, the UN security council adopted an embargo on unofficial diamond exports from Angola, in the hope of cutting off a valuable source of funding for Unita.

But Global Witness says its investigations show that Unita is still exporting significant quantities of diamonds, flying them out to neighbouring countries such as Zambia.

Charmaine Guise: "It is really business as usual"

Ms Guise said: "Because Unita have had a lot of warning that this embargo would be put in place they have been able to adjust their routes.

"Although we see a continuation of some land export routes and continued use of middlemen, who are involved in moving diamonds from one place to another, we also see a lot of flights in and out of Angola."

Change needed

The report accuses the Belgian authorities of failing to rigorously enforce the embargo in Antwerp, one of the world's major diamond trading centres.

Angolan diamonds are some of the best in the world and they are highly sought after on the international market.

A spokesman for De Beers, a dominant force in the diamond trade, says the company has instructed its buyers not to buy stones which could have come from Unita.

But Global Witness says, with little transparency and many middlemen, a fundamental change to the way the diamond industry operates is needed so that it no longer plays a role in fuelling conflicts in countries such as Angola and Sierra Leone.