The UN atomic watchdog called on Iran Monday to clear up allegations that it had been involved in nuclear warhead studies, while Tehran protested it has not seen any evidence backing up the charges.

Instead of simply dismissing the allegations as "forged" and "fabricated", Iran "should clarify the extent to which the documentation is factually correct and where, as it asserts, such information may have been fabricated or relates to non-nuclear purposes," IAEA chief Mohamed ElBaradei said.

Iran should provide "substantive information to support its statements and access to relevant documentations and individuals," ElBaradei told the International Atomic Energy Agency's 35-member board.

In a report last week, ElBaradei had accused Iran of stalling an UN investigation into its disputed nuclear programme.

After six years of intensive investigation, the IAEA still has not been able to determine whether the activities are entirely peaceful, as Iran claims.

The current main sticking point is the "alleged studies", referring to documentation found on a laptop in Iran which suggests Tehran may have been trying to develop a nuclear warhead, convert uranium and test high explosives and a missile re-entry vehicle.

Iran has consistently dismissed the allegations as "baseless" and the documentation used to back them up as "fabricated".

But the IAEA insists the onus is on Tehran to disprove the allegations.

Speaking to reporters on Monday, Iran's envoy to the IAEA, Ali Asghar Soltanieh, complained that Iran had not been allowed to see any of the documentation supposedly backing up the allegations.

"How come we can question a country without giving authentic documents? A member state is accused by another member state, but that member state has not been given any documents or evidence," he said.

It was Washington, not Tehran, that had created the current impasse, Soltanieh said.

ElBaradei also urged "member states which provided the agency with documentation related to the alleged studies to authorise the agency to share it with Iran."

The director general assured Iran that the IAEA was not trying to "pry" into its conventional or missile-related military activities, which do not come under the agency's jurisdiction.

"We need, however, to make use of all relevant information to be able to confirm that no nuclear material is being used for nuclear weapon purposes."

A senior Western diplomat, speaking on condition of anonymity, said Soltanieh was "trying to divert attention from the real problem -- Iran's failure to cooperate with the IAEA."

"Iran has had ample opportunity to study the documents and information gathered by the (IAEA's) safeguards department," the diplomat said.

ElBaradei also talked about Syria, which the United States alleges had been building a secret nuclear facility until it was destroyed in a bombing raid by Israel last year.

The IAEA had not yet analysed and evaluated samples taken during an IAEA visit to Al-Kibar in a remote desert area of northeastern Syria on the Euphrates River, ElBaradei said.

"Samples taken from the site are still being analysed and evaluated by the agency, but so far we have found no indication of any nuclear material," he said.

Turning to North Korea, the director general revealed that Pyonyang had asked the IAEA to remove seals and surveillance equipment from its Yongbyon nuclear plant.

"This morning, the DPRK (North Korea) authorities asked the Agency's inspectors to remove seals and surveillance equipment to enable them to carry out tests at the reprocessing plant, which they say will not involve nuclear material," ElBaradei said.

Pyonyang said last week that it was working to restart its atomic reactor at Yongbyon and no longer wanted US concessions promised under a landmark deal in June in return for its denuclearisation.

The hardline communist regime stopped work to disable its Yongbyon complex last month and said last Friday that it was working to restart the plutonium-producing reactor.

North Korea is angry that the United States has failed to drop it from a terrorism blacklist in return for the disablement work.

IAEA inspectors "have observed ... that some equipment previously removed by the DPRK during the disablement process has been brought back," ElBaradei said.

Nevertheless, "this has not changed the shutdown status of the nuclear facilities at Yongbyon," he added.