Iran has begun installing 6,000 new centrifuges at its main nuclear site in Natanz, state media quoted President Mahmoud Ahmadinejad as saying.

He made the comments during a visit to mark Iran's national nuclear day.

Iran is already thought to have some 3,000 centrifuges - which are used to enrich uranium - at the Natanz plant.

The US and Western allies accuse Iran of wanting to enrich uranium to build nuclear weapons, but Iran vehemently denies this.

Iran says it is enriching uranium for a civilian nuclear energy program and has continued to defy the UN Security Council's demand that it cease enrichment.

Last month, the Council approved a third round of sanctions against Iran.

Iran's national nuclear day commemorates the April 2006 anniversary of its first production of uranium that was sufficiently enriched to make atomic fuel.

PHOTO CAPTION

A general view of the Iranian nuclear power plant of Natanz.

BBC