By Maria Golovnina
LONDON, Oct 17 (Reuters) - Terrorist groups trying to get hold of nuclear weapons on the black market are becoming more sophisticated and the world needs to do more to prevent sensitive material from falling into their hands, the U.N. nuclear chief said on Wednesday.
Addressing the Chatham House think tank in London, International Atomic Energy Agency chief Yukiya Amano said one of the main risks was that militants could detonate a so-called nuclear "dirty bomb" to contaminate a major city.
"Terrorists (gaining) access to nuclear material is a real threat ... The amount (trafficked illicitly) is small but they are getting more and more professional," Amano said.
The IAEA's Illicit Trafficking Database, which monitors theft and other unauthorised activities involving nuclear and radioactive materials, contains more than 2,200 incidents registered since it was set up in 1995, he said.
Global powers have long warned of the growing threat of nuclear terrorism and urged closer cooperation to prevent acts of sabotage against nuclear materials.
A deepening confrontation between Iran and the West over Tehran's nuclear programme has intensified the debate nuclear security, with some experts predicting that Israel could launch a military strike to stop Iran developing a nuclear bomb.
Nuclear experts say much of the world's smuggled nuclear material is traceable to stockpiles in Russia and other former Soviet nations where many ageing Soviet-era reactors and research facilities remain poorly guarded.
Amano said more needed to be done to stop illicit nuclear trafficking.
"This is a real threat. We need to collect information, we need to analyse it. We have to train people and we have to provide equipment," Amano said.
"Most of these (incidents) are very minor but some are very serious."
A so-called dirty bomb can combine conventional explosives such as dynamite with radioactive material.
Experts describe the threat of a crude fissile nuclear bomb, which is technically difficult to manufacture and requires hard-to-obtain bomb-grade uranium or plutonium, as unlikely but with the potential to cause large-scale harm to life and property.
But a dirty bomb, where conventional explosives are used to disperse radiation from a radioactive source, is what is known as a "high probability, low consequence act" with more potential to terrorise than cause large loss of life. (Writing by Maria Golovnina; Editing by Alison Williams)