TEHRAN - The head of the UN atomic watchdog held talks Sunday with top officials in Tehran about unresolved concerns over previous "possible military dimensions" to Iran's nuclear programme.

International Atomic Energy Agency chief Yukiya Amano's visit comes as a December 15 deadline looms for completion of its long-running inquiry into allegations that at least until 2003, Iran conducted research into how to build a bomb.

Iran has said the accusations - including that it carried out explosives tests at the Parchin military base - are groundless and based on malicious intelligence provided by its enemies.

Amano held talks with Foreign Minister Mohammad Javad Zarif and President Hassan Rouhani as well as atomic agency chief Ali Akbar Salehi. Under a deal sealed in July with six world powers aimed at ending a 13-year standoff, Iran agreed to curbs on its nuclear activities that experts say would make any dash to produce a weapon all but impossible.

Amano also addressed a 12-member committee set up by the Iranian parliament to examine the deal but the meeting was held behind closed doors.

Rouhani was quoted by the official IRNA news agency as telling Amano that Iran would implement the deal, known as the Joint Comprehensive Plan of Action (JCPOA), and "we hope that you will fairly supervise the accord's implementation".

"We do not seek any demand beyond the safeguards agreement between Iran and the agency," Iran's president added, referring to IAEA verification measures, arguing that the "legitimacy of Iran's peaceful nuclear activities had been proven under past supervision".

Rouhani also said Iran was committed to voluntary implementation of an additional protocol under which the IAEA is granted access and information about states' nuclear sites.

As of June 2015, additional protocols were in force with 126 countries and another 20 are signatories but have yet to bring it into force, according to the IAEA.

Ahead of Amano's visit, the IAEA said the discussions in Tehran would "focus on... clarification of past and present outstanding issues regarding Iran's nuclear programme."

On September 9, the UN agency said Iran must resolve ambiguities over its past nuclear activities before crippling UN and Western sanctions can be lifted.

The IAEA will also have the task of confirming that Iran has scaled down its nuclear activities in accordance with the deal struck with Britain, China, France, Russia and the United States plus Germany.

Iranian lawmakers are in the final stages of reviewing the text of the nuclear agreement. It is not clear if there will be a parliamentary vote.

Earlier this month in the United States, the Republican-led House of Representatives rejected the nuclear deal in a purely symbolic vote held a day after the Senate cleared the way for the accord to come into force.