The three European signatories to the 2015 nuclear deal with Iran said they were "united in underlining the dangerous nature of this decision", reported AFP.
"It will significantly constrain the IAEA (International Atomic Energy Agency's) access to sites and to safeguards-relevant information," they added.
"We urge Iran to stop and reverse all measures that reduce transparency and to ensure full and timely cooperation with the IAEA," the UK, France and Germany said.
The statement came a day after the Islamic Republic ended the implementation of the Additional Protocol of the 2015 nuclear deal that allows the IAEA to carry out snap-inspections at sites not declared to the agency.
On Sunday, IAEA chief Rafael Grossi visited Tehran, where he reached a deal with Iran to continue some verification and monitoring activities in the country but in a more limited way.
Iran’s move appear to be meant to apply pressure on US President Joe Biden to rejoin the 2015 deal from which former President Donald Trump withdrew in 2018.
On Friday, the White House said that the US has accepted Europe's offer to mediate conversations with Iran regarding the 2015 nuclear deal.
Iran has said it is studying a European Union proposal for an informal meeting with the US.
