The report by the International Atomic Energy Agency said Iran had sharply increased its stockpile of uranium enriched to up to 60 percent, close to the roughly 90 percent level needed for atomic weapons.

Iran's total amount of enriched uranium now exceeds 45 times the limit authorised by a landmark 2015 agreement with world powers, and is estimated at 9,247.6 kilograms, according to the confidential IAEA report seen by AFP.

Iranian Foreign Minister Abbas Araghchi said in a statement he had told IAEA chief Rafael Grossi in a phone call that "Iran will respond to any inappropriate action by the European parties" to the 2015 agreement, referring to Britain, France and Germany.

The European trio have warned they could reimpose sanctions if Iran's nuclear programme threatens the continent's security.

Araghchi urged Grossi in their Saturday call to stop "parties from exploiting" the nuclear watchdog report "to advance their political objectives", according to the statement.

Iran rejected the IAEA report, the latest move in years-long efforts to restrict its nuclear activities over fears that it is seeking to develop nuclear weapons.

The Islamic republic has denied seeking nuclear arms and says it needs the uranium for civilian power production.