An international watchdog aiming to prevent the theft from nuclear sites of material that could be used in terrorist attacks has been launched.
The World Institute for Nuclear Security (WINS), which will be based in Vienna, Austria, will seek to prevent the material falling into the wrong hands.
It will work alongside the International Atomic Energy Agency in seeking to improve world nuclear security.
Mohamed ElBaradei, the IAEA director, said: "We have come to realise we have to become more intelligent and act in a preventative way" against terrorist groups seeking to steal nuclear materials and technology.
Internationally there are about 200 reports of radioactive material going astray every year, and many more incidents involving break-ins. Last November saw a break-in at the Pelindaba nuclear site in South Africa, where enough enriched uranium to make several nuclear bombs is stored.
The South African government said that the intruders, who were in two teams, "had prior knowledge of the electronic security systems" and were "technically sophisticated".
There is particular concern among western governments regarding the security of materials that were used to make atomic bombs in former Soviet republics.
Sam Nunn, the founder of the Washington-based Nuclear Threat Initiative (NTI), which has provided funding for WINS, said: "We're doing a better job controlling nuclear materials than 10 years ago, but this is not something we can ever declare victory over as long as the atom is with us."
Charles Curtis, the president of NTI, said: "Global nuclear security is only as strong as the weakest link in the chain. We can't afford to wait for a security Chernobyl before we act."
Funding for WINS has also come from the US Energy Department and the Norwegian government.