Iran on Sunday described a blackout at its underground Natanz atomic facility an act of “nuclear terrorism,” raising regional tensions.

Ali Akbar Salehi, the head of the Atomic Energy Organization of Iran, stopped short of directly blaming anyone for the incident. Details remained few about what happened early Sunday morning at the facility, which initially was described as a blackout caused by the electrical grid feeding the site.

Many Israeli media outlets offered the same assessment that a cyberattack darkened Natanz and damaged a facility that is home to sensitive centrifuges. While the reports offered no sourcing for the evaluation, Israeli media maintains a close relationship with the country’s military and intelligence agencies.

If Israel caused the blackout, it further heightens tensions between the two nations, already engaged in a shadow conflict across the wider Middle East.

IRAN’S NATANZ NUCLEAR FACILITY SUFFERS ELECTRICAL PROBLEM: STATE TV

It also complicates efforts by the U.S., Israel’s main security partner, to re-enter the atomic accord aimed at limiting Tehran’s program so it can’t pursue a nuclear weapon. As news of the blackout emerged, U.S. Defense Secretary Lloyd Austin landed Sunday in Israel for talks with Prime Minister Benjamin Netanyahu and Israeli Defense Minister Benny Gantz.