Iran has cancelled the accreditation of an International Atomic Energy IAEA inspector who was prevented from entering a nuclear facility last week.
The Atomic Energy Organisation of Iran AEOI said an alarm was triggered when the woman went through screening at the Natanz uranium enrichment plant.
Officials feared she was carrying “suspicious material”, it added.
There was no comment from the IAEA, which is in charge of monitoring Iranian compliance with a nuclear deal.
The announcement came as Iran rolled back another commitment under the 2015 accord by resuming enriching uranium at its underground Fordo facility. Enriched uranium can be used to make reactor fuel but also nuclear weapons.
Sanctions by US president
It is the fourth such step Iran has taken in response to the sanctions reinstated by US President Donald Trump when he abandoned the nuclear deal last year.
Under the accord, Iran agreed to limit its sensitive nuclear activities and allow in international inspectors in return for the lifting of crippling economic sanctions.
Mr Trump wants to force Iran to negotiate a new agreement that would place indefinite curbs on its nuclear programme and also halt its development of ballistic missiles. But Iran has so far refused.
The other parties to the deal, the UK, France, Germany, China and Russia have tried to keep it alive. But the sanctions have caused Iran’s oil exports to collapse and the value of its currency to plummet, and sent its inflation rate soaring.
The incident at Natanz seems to be the first of its kind since the nuclear deal was implemented.