UN experts on Sunday were inspecting Iran's controversial second uranium enrichment plant to verify whether the newly disclosed facility was designed for peaceful nuclear purposes.
Inspection of the plant, being built inside a mountain near the Shiite holy city of Qom, came as US President Barack Obama garnered support from France and Russia for a separate UN-brokered deal to end the crisis over Tehran's atomic programme.
A four-member team of International Atomic Energy Agency (IAEA) inspectors arrived in Tehran early today and later began inspecting the facility which is being constructed adjacent to a military base south of the capital.
"They are currently doing their job," Ali Shirzadian, spokesman of Iran Atomic Energy Organisation, told AFP without offering details.
Iran's disclosure to the IAEA of the Qom plant's existence on September 21 sparked a wave of global outrage, with Obama warning the Islamic republic would face "increased pressure" if it fails to come clean on its atomic ambitions.
Iran has already been enriching uranium -- the most controversial aspect of its nuclear project -- for several years at another plant in the central city of Natanz, in defiance of three sets of UN sanctions.