The head of the UN atomic agency has rejected as "baseless" Iranian accusations that the watchdog has been infiltrated by "saboteurs and terrorists."

"If I give a response it is very simple: it is baseless," International Atomic Energy Agency chief Yukiya Amano said in an event in London, a recording of which was provided to AFP on Thursday.

He said that he had not responded earlier because he had not wanted to "dignify" the comments made in a speech at IAEA headquarters in Vienna on September 17 by Iran's nuclear chief Fereydoon Abbasi Davani.

"Sometimes it is not useful to dignify these claims with official answers," the Japanese told the event on Wednesday organised by the Chatham House think-tank.

Last November the IAEA published a raft of what it called "credible information" indicating that prior to 2003, and possibly since, Iran had carried out "activities relevant to the development of a nuclear explosive device."

Tehran has rejected the claims as being based on forgeries provided by its enemies and denies working, or ever having worked, on developing nuclear weapons.

It says that its activities are for peaceful purposes but the IAEA, which conducts regular checks on Iran's nuclear facilities, says that because of a lack of cooperation it cannot be certain that this is the case.

Multiple UN Security Council resolutions have called on Iran to suspend the most sensitive parts of its nuclear work, in particular uranium enrichment.

Amano also said Wednesday that he was ready to hold talks with Iran about the claims set out in the November report, even including going to Tehran if such a trip produced "concrete results."

A string of such meetings over the past year, the last one on August 24 in Vienna, have been fruitless, however, as was a visit by Amano to Tehran in May.

The agency in particular wants Iran to grant access to the Parchin military base near Tehran which it visited twice in 2005 but wants to look at again.

Western nations have accused Iran of removing evidence of past suspected weapons research activities at Parchin.

"They are undertaking quite intensive activities at Parchin," Amano said on Wednesday.

"We cannot draw conclusions at this stage but it is very obvious to us (that) we need to seek clarification from Iran ... We keep on making requests."

Amano also said that the IAEA was not making any contingency plans to evacuate its personnel from Iran in the event of a military attack by Israel and/or the United States.

"A possible attack by Israel is a hypothetical scenario and we are not working on hypothetical scenarios," Amano said.

The agency has no staff permanently based in Iran but its inspectors carry out frequent visits to Iran's nuclear facilities including at the Fordo and Natanz enrichment plants, prime targets in any strike.

Unless the agency is given prior notice of any military action -- as happened in a late-night phone call in the case of Iraq in 2003 -- its staff could conceivably be in danger, experts say.

The IAEA's next report detailing the latest advances in Iran's nuclear programme is expected in mid-November.