Iran apparently had the help of a noted Russian scientist in developing a detonator and high explosives for its nuclear programme, a Washington-based non-governmental group has said.

The Institute for Science and International Security (ISIS) identified Russian scientist Vycheslav Danilenko as having had the know-how to help Iran weaponise its atomic programme in a report released on Sunday.

It based its conclusion on the findings issued last week by the UN watchdog, the International Atomic Energy Agency (IAEA), which expressed serious concerns about “credible” evidence of Iran working towards the development of nuclear warheads to fit inside its medium-range missiles.

The IAEA said there were “strong indications that the development by Iran of the high explosives initiation system, and its development of the high speed diagnostic configuration used to monitor related experiments were assisted by the work of a foreign expert.”

The expert “was not only knowledgeable in these technologies... (but) worked for much of his career with this technology in the nuclear weapon programme of the country of his origin,” the IAEA said.

“Given his background and experience, this ex-Soviet nuclear weapons expert was well versed in key aspects of developing nuclear weapons,” the ISIS report said, adding that Mr Danilenko also has experience “in the important area of the diagnostics of high explosions”.

The ISIS report noted that according to the IAEA Mr Danilenko contacted the Iranian embassy in mid-1995, offering his particular expertise in producing ultra-dispersed diamonds (UDD or nanodiamonds).