One could have suspected this is so, but now there seems to be a smoking gun (or rather, smoking implosion mechanism).
Iran is currently conducting research and development on nuclear weapons, an exiled opposition group claimed Friday in Paris - identifying two locations near Tehran where such work is allegedly taking place.
"This site and centre are the locations for research and production of the explosion system of an atomic bomb, which is one of the most important aspects of the mullahs' nuclear weapons project," Mehdi Abrishamchi, an official of the National Council of Resistance of Iran (NCRI) said, referring to Iran's clerical leaders.
In contrast, U.S. intelligence agencies have concluded that the Islamic state probably ended weapons-related work in 2003.
The International Atomic Energy Agency (IAEA) has received intelligence information indicating that such research could have been conducted in the past, but has not drawn a final conclusion to confirm this.
The ongoing efforts were being conducted by an entity called Research Centre for Explosion and Impact (MEFTAZ), affiliated with the Defense Ministry and housed in an unmarked building in Tehran, Abrishamchi said at a press conference.
Among other tasks, that centre was working on computer simulations, he said.
The Paris-based NCRI also alleged that there was a second site near Sanjarian village for building technical components and testing high explosives.
In nuclear weapons, high explosives are placed around a core of nuclear material and triggered simultaneously in order to implode the core and cause a nuclear chain reaction.
Iranian officials have told the IAEA that they experimented with simultaneous detonators in the past, but said the work was done for civilian rather than military use.
A diplomat close to the Vienna-based agency said its inspectors had not found anything suggesting ongoing Iranian efforts in that field.
Tehran's leaders say they have no interest in nuclear energy except for electricity generation and other peaceful uses.
The Paris-based NCRI made its allegations one week before Britain, China, France, Germany, Russia and the United States are scheduled to hold talks with Iran in Geneva, where the world powers expect a serious response to their concerns over Iran's nuclear program.
The NCRI is considered the political wing of the People's Mujahedin of Iran, a group that seeks to overthrow Iran's clerical regime.
In 2002 the NCRI played an important role in revealing Iran's nuclear program, which Tehran had kept secret from IAEA inspectors. Later claims regarding Iran's nuclear activities failed to be equally substantial.
Abrishamchi said the information was collected by dozens of sources of the Muhajedin in Iran.