Iranian hackers broke into the computer systems of the International Atomic Energy Agency (IAEA), the UN agency said on Tuesday.
According to a statement released by the organization, security experts have indicated that hackers originating in Iran were responsible for breaking into the IAEA’s systems and publishing sensitive and confidential material.
The announcement came after a group posted contact details for more than 100 experts working for the UN nuclear watchdog two days ago.
The group calls itself "Parastoo"— a Farsi word meaning the swallow bird and a common name for girls in Iran.
IAEA spokeswoman Gill Tudor said that the IAEA "deeply regrets this publication of information stolen from an old server."
She added the server had been shut down some time ago and agency experts had been working to eliminate any "possible vulnerability" in it even before it was hacked.
The IAEA was doing "everything possible to help ensure that no further information is vulnerable," said Tudor.
The announcement of the hacking came several hours after a report indicated that Iran is planning to build a nuclear bomb with at least triple the force of the bomb that destroyed Hiroshima in World War II.
The report was based on diagrams obtained by the Associated Press and which were first discovered by IAEA scientists after an inspection of an Iranian nuclear facility.
The document was published by the AP Tuesday after, the news agency said, it was leaked by officials critical of the way the West has been handling the Iran issue.
The diagrams discovered by the IAEA show Iranian scientists calculating the desired "nuclear explosive yield" in a device they were apparently working on. IAEA inspectors described the diagrams in a report, and a senior official who is working with the Geneva-based UN organization confirmed that the diagrams obtained by AP were the same ones mentioned in the report.
The UN atomic agency said earlier this month it will hold in December its first talks with Iran since August over Tehran's nuclear program.
The IAEA wants Tehran to address evidence it says it has suggesting that until 2003, and possibly since, Iran conducted research work "relevant to the development of a nuclear explosive device."
Parallel diplomatic efforts by six world powers have been aimed at persuading Iran to scale back parts of its current nuclear program because of suspicions that its wants a nuclear bomb.
Iran has rejected the IAEA’s information, set out in a major report a year ago, as based on forgeries provided by its enemies. In September Iran's atomic chief accused the agency of being infiltrated by "terrorists" and saboteurs.
Iran has also accused the nuclear agency of sharing its classified information with Israel.
IAEA chief Yukio Amano recently told the UN General Assembly that Iran is not cooperating with its investigation.