Iran has agreed to allow UN inspection of the Parchin complex, a military site about 30 km south of Tehran, the UN nuclear watchdog said Wednesday.

"We haven't stumbled on any weaponization activities, although we are trying to visit different sites, including military sites," head of the International Atomic Energy Agency (IAEA) Mohamed ElBaradei said Wednesday.

In the next few days or weeks UN inspectors will visit the Parchin site as part of the UN investigation into allegations that Iran has carried out work linked to the development of nuclear weapons., ElBaradei said.

ElBaradei said the key issue is the production of highly-enriched uranium or plutonium, materials that can be used to fuel a nuclear bomb.

The United States and several other countries said in September last year that Parchin may be a site where Iran was testing explosives for an atom bomb.

Tehran insists its nuclear program is for peaceful use only.