The U.N. nuclear agency's deputy chief arrived in Tehran on Monday for talks with Iranian officials about persistent allegations that the Islamic republic is running a covert nuclear weapons program, the official IRNA news agency reported.

IAEA Deputy Director-General Olli Heinonen's discussions Monday with Iranian officials are expected to focus on allegations that Iran is testing powerful explosives and seeking to design a missile re-entry vehicle,two features which could have use for nuclear weapons.

Iran dismisses as "fabricated" the allegations raised by U.S. intelligence agencies and insists its nuclear program is purely peaceful and geared solely toward producing electricity. The United States and some of its allies contend that Tehran has been trying to gain nuclear weapons capability.

A prominent Iranian hard-liner and aide to Iran's top spiritual leader denounced his government for hosting Heinonen, saying the trip was part of a "joint U.S.-Israeli trick" aimed at strengthening allegations that Iran is pursuing nuclear weapons.

"It is a trick that looks ridiculous," Hossein Shariatmadari wrote Monday of Heinonen's trip in his conservative daily Kayhan.

Heinonen, during a closed-door meeting of the International Atomic Energy Agency in February, offered detailed information provided by Western intelligence agencies suggesting that Iran could have been studying how to use enriched uranium to build atomic bomb.

"Heinonen opened the first act of this ridiculous play, written by Mossad and directed by the U.S., at the (IAEA) board of governors. Now, he is to perform the second act during his (Iran) trip. It is deploring and surprising that our nuclear officials have agreed to Heinonen's trip to Iran," said Shariatmadari, a representative of Iran's top leader Ayatollah Ali Khamenei.

IRNA said Heinonen would hold talks with Javad Vaeedi, a top nuclear negotiator who heads the Iranian negotiating team, during his two-day visit to Iran.