In the aftermath of Iranian drone and missile attack on Israel as a response to Israeli raid on the Iranian consulate in Syria two weeks ago, the United Nations nuclear watchdog chief has expressed concerns over Israel's next possible move.

The UN Atomic Watchdog has warned that Israel may possibly be targeting Iranian nuclear facilities.

Meanwhile, Israel's military chief on Monday announced that they would retaliate against the Iranian attack.

Iran had on April 13 fired around 300 Iranian drones and missiles in retaliation for a suspected Israeli airstrike on its embassy compound in Syria's Damascus on April 1, which left two top Iranian Generals dead.

This comes amid calls by allies to restore peace in the region and to avoid an escalation of conflict in the Middle East.

IAEA Director General Rafael Grossi claimed that Iran had shut its nuclear facilities on Sunday over "security considerations" and that while they reopened on Monday, he kept IAEA inspectors away "until we see that the situation is completely calm."

"We are going to resume tomorrow," news outlet Reuters quoted Grossi as saying. "This has not had an impact on our inspection activity," he added.

Grossi expressed that there can be a possible attack by Israel on Iran's nuclear facilities but he urged Israel to practice "extreme restraint."

The atomic watchdog regularly inspects Iran's main nuclear facilities like its enrichment plants at Natanz that are at the heart of the country's nuclear programme.

Iran says its nuclear programme is entirely peaceful, but Western powers accuse Tehran of seeking to develop nuclear bombs.