Global environmental crime is worth up to $213 billion a year and helping to finance criminal and terrorist groups threatening security and sustainable development worldwide, according to a report released Tuesday by the UN and Interpol.

The report said Somalia's Al-Qaeda-linked Shebab rebels were estimated to make between $38 and $56 million (28 to 41 million euros) per year from the illegal trade in charcoal, and that ivory from poached elephants was the primary source of income for Uganda's Lord's Resistance Army (LRA).

Ivory poaching was also carried out by rebel groups including insurgents in Central African Republic and Democratic Republic of Congo, as well as the fearsome Janjaweed -- who carried out atrocities in Sudan's Darfur region -- operating also in Niger and Chad.

"The illegal trade in wildlife and environmental crime are now widely recognised as significant threats on a global scale, to be tackled with urgency," said Achim Steiner, head of the United Nations Environment Programme (UNEP).

"Beyond immediate environmental impacts, the illegal trade in natural resources is depriving developing economies of billions of dollars in lost revenues just to fill the pockets of criminals," he said.

The report was released as part of a week-long global environment conference at UNEP's Nairobi headquarters aimed at tackling challenges from poaching to marine pollution and boosting the "green economy".

"Sustainable development, livelihoods, good governance and the rule of law are all being threatened, as significant sums of money are flowing to militias and terrorist groups," he added.

"While there is growing awareness, the responses to date in terms of impact have not been commensurate with the scale and growth of the threat to wildlife and the environment."

The meeting in the Kenyan capital, the first ever United Nations Environment Assembly (UNEA), comes amid tight security in the Kenyan capital, after a series of warnings of the threat of attack by Somalia's Shebab.