The U.S. ambassador to the United Nations nuclear watchdog walked out of an agency meeting on Wednesday in protest when Iran’s representative accused Washington’s ally Israel of “genocide”, diplomats said.

Officials from Canada and Australia also left the closed-door meeting of the International Atomic Energy Agency’s (IAEA) 35-nation governing board when Iran’s Ali Asghar Soltanieh made his statement during a debate on Syria, they said.

They later returned to the closed-door IAEA meeting, where such action is unusual though it has happened before in other international forums.

Soltanieh was not immediately available for comment. Iran has often criticized Israeli policies towards the Palestinians. It has also said Israel would be wiped “off the face of the earth” if the Jewish state attacked it.