The decision means that international inspectors will not be able to oversee sites. Experts have warned that Tehran could revive plans to build a bomb.
Iranian officials criticized Rafael Grossi, the head of the International Atomic Energy Agency, for saying that there was no evidence of a systematic effort to build nuclear bombs only after Israel began its military attacks.
Iranian authorities are sweeping up hundreds of people deemed suspected spies or infiltrators. Some worry the campaign could become a broader crackdown on political opponents and minorities.