Iran confirmed that it has begun uranium enrichment at an underground bunker of the Fordo nuclear facility, Iranian diplomats on Monday said at the International Atomic Energy Agency (IAEA)'s headquarters.

The nuke work would be supervised by the IAEA, the TV channel AL-Alam quoted Ali Asghar Soltanieh, Iranian representative at the UN nuclear watchdog.

The nuclear plant was built near the Shiite holy city of Qom, which was used for producing up to 20 percent enriched uranium. It was kept secret and wasn't acknowledged by Iran until the identification by Western intelligence agencies in 2009.

The start of the nuke work at the Fordo site has increased international fear as the West suspects that Iran's uranium enrichment may be meant for moving closer to the ability to make nuclear weapons. But Iran insists that its nuclear program is only for the purpose of peaceful use.