Iran's ambassador to the United Nations nuclear watchdog said on Tuesday that the Islamic Republic would take part in a proposed international conference in December on creating a nuclear-free zone in the Middle East.

"The Islamic Republic of Iran now finally has decided to participate at the conference in Finland, in Helsinki, in December on a Middle East [nuclear] free zone," Ali Asghar Soltanieh, Iran's ambassador to the International Atomic Energy Agency, told reporters in Brussels where he attended a seminar on nuclear non-proliferation.

Soltanieh's came only one day after UN nuclear chief Yukia Amano said that Iran was not cooperating with an investigation into suspected secret work on nuclear weapons.

Amano told the UN General Assembly on Monday that talks between the International Atomic Energy Agency and Iran have intensified this year.

"However, no concrete results have been achieved so far," he said.

In his annual report to the world body, Amano said he also remains "seriously concerned" about North Korea's nuclear program, calling its statements about uranium enrichment activities and the construction of a light water reactor "deeply troubling."

He also urged the Syrian government to respond to questions about a building destroyed by Israeli warplanes in the Syrian desert in 2007 which the IAEA says was "very likely" the covert site of a nuclear reactor.

Last week, Iran confirmed for the first time that it has finished installing centrifuges for enriching uranium at its underground nuclear facility in Fordow.

The head of Iran's Atomic Energy Organization, Fereydoun Abbasi, told Iran' Fars news agency on Thursday that "Iran is completing its nuclear activities regardless of the negative Western media speculations and reports." Abbasi spoke to reporters after a cabinet meeting in Tehran.