Iran carried out secret nuclear activities with material not declared to the UN nuclear watchdog at three locations that have long been under investigation, the watchdog said in a wide-ranging, confidential report to member states seen by Reuters.

Iran's foreign ministry and the Iranian nuclear agency rejected the report, calling it "politically motivated" in a joint statement.

The agency mentions secret nuclear activities conducted with undeclared materials at three sites under investigation, describing the situation as a 'serious concern'