The International Atomic Energy Agency (IAEA) had warned Saturday that the "disproportionate and unprecedented" move to bar inspectors would seriously hamper its work in Iran.

Iranian media and a Western diplomat said the decision concerned eight inspectors, all from France and Germany.

"Iran must immediately reverse these inspector de-designations and fully cooperate with the Agency to enable them to provide assurances that Iran's nuclear programme is exclusively peaceful," the permanent representatives to the IAEA of France, Germany, the United Kingdom, and the United States said in a joint statement.

The four countries "will continue to stand in strong support of the IAEA and the international safeguards verification regime on which the world's security relies," it added.

IAEA head Rafael Grossi on Monday also urged Iran to reconsider its decision, warning that Iran's failure to cooperate would carry severe consequences.

"If they do not cooperate with the IAEA, they will not get what they want: the assurances they want to see, the confirmation they want to see, the approval of the international community," Grossi told AFP in an interview.

Brussels, which acts as coordinator for the 2015 nuclear deal between Tehran and world powers known as the JCPOA, on Sunday said it was "highly concerned" by the development.

In 2015, major world powers reached the accord with Iran under which Tehran would curb its nuclear programme in exchange for relief from crippling economic sanctions.

But that started to unravel in 2018 when then-US president Donald Trump withdrew from the deal and reimposed sanctions.

Tehran in turn stepped up its nuclear programme, while continuing to deny that it harbours ambitions of developing nuclear weapons capability.

Efforts to revive the deal have been fruitless so far.