It was the first acknowledgement from Tehran that it had answered the agency’s long-standing demands.
The head of Iran’s civilian Atomic Energy Organisation, Mohammad Eslami, said Iran sent the requested explanations on March 20 about former undeclared sites in Iran where there was evidence of past nuclear activity.
The deadline came as part of an agreement announced last month to resolve the problem of undeclared uranium particles in Iran by June — which has long been a source of tension between Tehran and the UN atomic watchdog.
The issue is separate from now-stalled talks to revive Tehran’s nuclear deal with world powers, which collapsed four years ago when former President Donald Trump withdrew the US from it and imposed crushing sanctions on Iran.
In the meantime, Iran has vastly expanded its nuclear work.
As the fate of a renewed nuclear deal hangs in the balance, long-sought answers about Iran’s old but undeclared nuclear sites would improve trust and solve a major sticking point in its talks with the International Atomic Energy Agency.
Mr Eslami said that Iran had handed over documents to the UN watchdog about the three requested sites in Iran.
He said he expected agency inspectors to visit Iran “to review the answers” and finish a report on the subject by late June.
The IAEA, based in Vienna, declined to comment on Mr Eslami’s remarks.
In 2019 it discovered the traces of man-made uranium that suggested they were once connected to Iran’s nuclear programme.
US intelligence agencies, western nations and the IAEA have said Iran ran an organised nuclear weapons programme until 2003. Tehran has denied ever seeking nuclear weapons.
As a member of the Nuclear Non-Proliferation Treaty, Iran is obliged to explain the radioactive traces and provide assurances that they are not being used as part of a nuclear weapons programme.
The IAEA has staked its credibility on finding information about the sites, with chief Rafael Grossi routinely criticising Iran for its failure to say where the radioactive particles came from and where they are now.
Mr Eslami on Wednesday claimed that one of the particles found by IAEA inspectors did not exist in Iran, without offering evidence or details.
He blamed regional arch-enemy Israel for “sowing doubts” about the nature of Iran’s nuclear programme.
Israel has said it believes Iran would try to develop a nuclear weapon, despite western intelligence assessments indicating otherwise.
Tehran now enriches uranium up to 60 per cent purity — its highest level ever and a short technical step from weapons-grade levels of 90 per cent, and far greater than the nuclear deal’s 3.67 per cent cap.
Its stockpile of enriched uranium continues to grow as nuclear talks in Vienna flounder, worrying nuclear experts that Iran could be closer to having enough material for an atomic weapon if it chose to develop one.