U.S. strikes on Iran this weekend likely inflicted "very significant damage" on three of its major nuclear facilities, the head of the United Nations-led International Atomic Energy Agency (IAEA) said Monday.

Speaking during an emergency gathering of the IAEA board of governors, Director-General Rafael Grossi stressed the impact hasn't been independently assessed underground because of the ongoing conflict.

"There needs to be a cessation of hostilities for the necessary safety and security conditions to prevail so that Iran can let IAEA teams into the sites to assess the situation," he said. "We continue to monitor the situation and encourage the Iranian regulator to........

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