The International Atomic Energy Agency (IAEA) said in a 13-page report released to diplomats in Vienna that it had "serious concern" over gaps in Iran's recent accounts of its activities.

The report was released days after US Secretary of State Colin Powell charged that Iran -- branded by Washington as part of "axis of evil" of states seeking nuclear arms -- was "still too slowly... coming forward with answers needed by the IAEA".

The IAEA last year accused Iran of lying to the world for 18 years over its nuclear operations, and says in its report that since then the Islamic republic has failed to declare that it has P2-centrifuges capable of making highly enriched uranium and explain its use polonium, an atomic combustible.

"The omission from Iran... to any reference to its possession of the P-2 centrifuge design drawings and associated research... is a matter of serious concern," it said.

"The basic technology is very similar (to that of Libya) and was largely obtained from the same sources," the UN nuclear watchdog said.

A Western diplomat familiar with the document said: "Iran was caught lying."

The report states that the discovery that Iran owns such a centrifuge "runs counter" to Iran's declaration in October last year that it had declared "the full scope" of its activities to the IAEA.

Facing threats of UN sanctions, Iran agreed that month to give full details of its nuclear programme to the IAEA and temporarily suspend uranium enrichment.

The IAEA's latest report, of which AFP has obtained a copy, says the agency needs "clarification (on) the nature and scope of Iran's activities in relation to P-2 centrifuges."

This would be needed to confirm Iran's claims that its programme is purely intended to produce electricity.

The IAEA document confirms news reports this week that inspectors have found evidence that Iran has produced polonium-210 (Po-210), an element used in the timing of nuclear explosions.

"The issue of the purpose of Iran's activities related to the production and intended use of Po-210 components remains a concern," it said.

Iran has owned up to experimenting with polonium but has offered an explanation involving the material's other possible uses, including power generation.

The IAEA complained however "of an absence of information to support Iran's statements in this regard."

The report also cast doubt on Iran's earlier protests that traces of highly-enriched uranium found at its nuclear facilities at Natanz and the Kalaye Electric Company must have entered the country on equipment bought on the black market.

It said the types of uranium differ, even though Iran insists that source in both cases was the same imported centrifuge components.

The agency ended its report with a call on Iran to "intensify its cooperation" with the body.

In Tehran, Iran's main conservative party set to lead parliament after sweeping elections, vowed Tuesday to continue to show "goodwill" to the IAEA, but reiterated that the country had a right to nuclear technology.

The IAEA said in its report it was probing the "supply and routes of such technology" as Iran and Libya has, as part of the quest to verify the two countries' claims on their nuclear programmes.

Iran's foreign ministry has said repeatedly that it does not know the source of the nuclear technology it bought.

But Malaysian police on Friday declared that the former head of Pakistan's nuclear programme, Abdul Qadeer Khan, sold nuclear centrifuge parts to Iran in the mid-1990s.

In Tripoli, IAEA chief Mohamed ElBaradei said Tuesday the agency was ready to help Libya develop its peaceful uses of nuclear energy following its decision in December to abandon programmes to develop weapons of mass destruction.

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