Iran on Monday accused Israel of orchestrating an attack on its main nuclear facility that stirred fears for the future of talks involving Washington and Tehran over a deal to constrain the Islamic Republic’s ability to produce a nuclear weapon.

The attack at Iran’s Natanz nuclear facility, which destroyed a number of centrifuges and caused an electricity blackout, occurred as U.S. Defense Secretary Lloyd Austin was visiting Israel and was preparing to meet with Israeli Prime Minister Benjamin Netanyahu.

Top Biden administration officials apparently were given no advance notice of the attack against the Iranian uranium-enrichment facility, according to people familiar with the situation.

Mr. Austin, asked about the attack before meeting Mr. Netanyahu, declined to address it and said only that U.S. diplomatic efforts, aimed at assuring Iranian compliance with terms of the 2015 nuclear agreement in exchange for easing U.S. sanctions, would continue.

The attack in Iran concerned European officials who remained party to the 2015 pact after the U.S. under former President Donald Trump withdrew from it.

European Union spokesman Peter Stano said there had been determination of the cause of the Natanz incident, but added: “We reject any attempts to undermine or weaken diplomatic efforts on the nuclear agreement.”

In Berlin, German Foreign Minister Heiko Maas said that talks last week in Vienna involving the U.S., Iran and other parties to the 2015 nuclear agreement had been constructive. Talks are scheduled to continue this week.

“What we hear coming out of Tehran is not a positive contribution, especially the developments taking place in Natanz,” he said, adding, “We don’t have our own insights” into what precisely happened.

Israeli officials have declined to comment on Sunday’s incident, although Israeli media has reported that the attack was carried out by its spy service Mossad.

In Washington, the White House said Monday that the U.S. had no involvement in the Natanz attack, adding there was no indication it would affect the continuing talks.

European officials expect the Vienna negotiations to resume this week, although there are concerns among the officials that the attack could further narrow the political tolerance for compromise in Tehran, complicating any agreement to restore the 2015 deal.

Iranian officials didn’t detail the nature or extent of the damage at Natanz.