NUCLEAR smugglers are operating around the world with impunity, according to research by the International Atomic Energy Authority, which warns that the risk of atomic terrorism against civilians has never been greater.

The biggest danger is not that a terrorist group will produce a 'suitcase bomb' - a self-contained portable nuclear weapon considered beyond the capabilities of independent organisations - but that they could set off a 'dirty bomb', a conventional bomb covered in highly radioactive material. This could contaminate a city or a region's water supply.

Authorities in former Soviet republics, such as Georgia and Kazakhstan, have recently seized quantities of plutonium and uranium from would-be smugglers - but the IAEA said that these cases could be the tip of the iceberg. You need eight kilos of plutonium or 25 kilos of enriched uranium to make an atomic bomb but the fact that these materials are in the black market at all is troubling, because it means that these people have access. John Large, a British independent nuclear consultant, said: "If one of these groups got a large enough amount of plutonium and got the explosion to vapourise it, so that it was spread widely, then a bomb set off on the top of Canary Wharf (the tower in east London) could contaminate everything for three kilometres around."

Building an atomic weapon is almost certainly beyond the capability of any independent group; even Saddam Hussein was unable to do so despite spending billions of dollars over 10 years on the project.

Though Iraq developed the detonation systems needed, it could not accumulate enough weapons-grade products to make a bomb. But that would not stop such groups using radioactive substances for a high-profile attack.

America currently monitors 130 terrorist organisations that it believes might use such weapons if they acquired them.

* Independent News Service

Charles Arthur in London