UN nuclear inspectors in Iran have stayed away from related facilities since Sunday, amid threats of an Israeli attack, the head of the UN nuclear watchdog, the IAEA said on Monday.

Rafael Grossi, director of the International Atomic Energy Agency, told reporters in New York that Iran had closed its nuclear facilities on Sunday over “security considerations.” While they reopened on Monday, Grossi said he kept IAEA inspectors away “until we see that the situation is completely calm.”

After Iran targeted Israel with a massive barrage of around 350 drones and missile on Saturday/Sunday night, Israeli leaders have vowed retaliation. The United States, European powers and some regional counties have urged Israel to exercise restraint, but Israel military and political officials have vowed to restore deterrence.

“We are going to resume tomorrow,” Grossi added. “This has not had an impact on our inspection activity.”

Asked about the possibility of an Israel strike on Iranian nuclear facilities, Grossi said, “We are always concerned about this possibility.” Grossi also urged “extreme restraint.”