The International Atomic Energy Agency says Iran has denied its inspectors access to a nuclear facility in the country.
The IAEA earlier this month received a pledge from Iran that it would cooperate in keeping data from surveillance cameras at nuclear facilities in the country.
In a report the UN nuclear watchdog sent to its members on Sunday, it was explained that inspectors were not allowed to visit a centrifuge component manufacturing workshop in Karaj on the outskirts of Tehran.
IAEA Director General Rafael Grossi expressed concern that Iran was in violation of its agreement with the agency.
Iranian Ambassador to the IAEA Kazem Gharibabadi tweeted that the report was not accurate. The post says the equipment is not included in the list of items subject to IAEA inspections.
The report noted that the inspectors paid a 3-day visit to Iran early last week. They were there to service IAEA monitoring equipment and to replace the data-storage units in cameras that monitor Iran's nuclear development activity.
Observers say that Tehran is stepping up its nuclear development in response to the continued imposition of US sanctions against the country. It is also curtailing the activities of IAEA inspectors, making it difficult for the UN agency to gain a comprehensive picture of Iran's nuclear program.