Olli Heinonen, the International Atomic Energy Agency's (IAEA) deputy director general, went into talks with Iranian officials mid-morning Tuesday after a first round on Monday, the state broadcaster reported.

No information has filtered out over the contents of the discussions so far and not even photographs or video footage of the meetings have been released.

Heinonon's two-day visit is aimed at pressing Iran over claims it has carried out so-called "weaponization studies", the Vienna-based watchdog has said.

It was not immediately clear which Iranian officials were taking part in Tuesday's talks.

The deputy head of Iran's atomic energy organisation Mohammad Saeedi and its ambassador to the IAEA Ali Asghar Soltanieh met Heinonen Monday but contrary to initial reports deputy national security chief Javad Vaeedi was absent.

No reason was given for Vaeedi's absence.

In a sign of the sensitivity of the talks, Iran's leading hardline daily Kayhan launched a withering personal onslaught against Heinonen and his intentions on Monday.

"This trip is to complete a joint Israeli-US trick to provide phoney proof on Iran's nuclear activities," said an editorial signed by chief editor Hossein Shariatmadari, who is appointed by supreme leader Ayatollah Ali Khamenei.

In a closed-door briefing to diplomats at IAEA headquarters in Vienna on February 25, Heinonen presented detailed evidence suggesting that Iran could have been studying how to use its nuclear technology to make a warhead.

Western diplomats present at the meeting subsequently said the new evidence of alleged "weaponization studies" was troubling.

Iran, which insists its nuclear programme is entirely peaceful and aimed solely at generating energy, at the time furiously denounced the claims as fake.

Iran's refusal to suspend sensitive uranium enrichment operations -- which the West fears could be used to make a nuclear weapon -- has already led to three sets of UN Security Council sanctions against Tehran.

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