IAEA Director General Yukiya Amano
IAEA Director General Yukiya AmanoReuters

The head of the UN atomic watchdog was granted access Sunday to a controversial Iranian military site where it is alleged covert research to build a nuclear bomb took place, AFP reported.

Yukiya Amano, chief of the International Atomic Energy Agency (IAEA), visited Parchin, a base east of Tehran as efforts are stepped up to resolve by year end "ambiguities" with Iran about past "possible military dimensions" of its nuclear program.

The original itinerary for Amano’s one-day visit to Iran did not include a visit to Parchin.

Iran has claimed that the allegations that it sought to build a bomb - including that it conducted relevant nuclear detonator tests at the covert Parchin military base - are groundless.

However, Iran last October admitted to using Parchin to test exploding bridge wires, used as nuclear detonators.

The IAEA has repeatedly asked for access to Parchin, requests that have constantly been denied. Under a controversial classified side deal with Iran, the IAEA will let the Islamic regime inspect Parchin itself with no international inspectors.

"Amano paid a formal visit to Parchin, and visited some workshops about which there has been some false information," Behrouz Kamalvand, a spokesman for Iran's Atomic Energy Organization, said Sunday, according to AFP.

The Vienna-based IAEA confirmed the site visit which is significant given that previous requests for access had been refused.

It comes as Iran and six world powers aim to implement a deal sealed in July aimed at ending a 13-year standoff over Tehran's nuclear activities.

A December 15 deadline looms for completion of the IAEA's long-running enquiry into allegations that at least until 2003, Iran conducted research into how to develop an atomic bomb.

The IAEA said recently that satellite imagery had shown the presence of vehicles, equipment and probable construction materials at the Parchin site, which American media reported as being suspicious and possible evidence of efforts to disguise past illicit activity.

Iran's UN mission called the reports "baseless", adding that construction work at the military complex, which also includes offices and residential buildings, is "quite normal".

Iranian Foreign Minister Mohammad Javad Zarif rejected the reports as well, saying they were “lies” spread by opponents of the nuclear deal with world powers and claiming the alleged “sanitization” at the site was simply “road construction”.

Amano earlier Sunday held talks with top Iranian officials about unresolved concerns over Iran's nuclear program, noted AFP.

He also met Foreign Minister Mohammad Javad Zarif and President Hassan Rouhani as well as atomic agency chief Ali Akbar Salehi.