Vienna: Iran is a "special case" because of concerns it may be working to develop an atom bomb, the UN nuclear watchdog chief said yesterday amid an Arab push to focus his agency's attention on Israel's presumed nuclear arsenal.

The Iranian ambassador to the International Atomic Energy Agency said Israel's nuclear capability was the bigger issue.

With the UN Security Council expected to vote on new Iran sanctions this week, IAEA Director-General Yukiya Amano highlighted Tehran's escalating uranium enrichment in defiance of UN resolutions demanding a halt and its failure to grant unfettered access to his inspectors and investigators.

"I also need to mention that Iran is a special case because, among other things, of the existence of issues related to possible military dimensions to its nuclear programme," he said, opening a meeting of the IAEA's 35-nation Board of Governors.

But the Iranian envoy said the Vienna-based agency should concentrate its non-proliferation efforts on Tehran's regional arch-foe Israel, which has not signed the Non-Proliferation Treaty (NPT) and is widely believed to have the only nuclear arsenal in the Middle East.

The debate followed a month-long UN conference in New York to review the NPT which put Israel in the spotlight, and at a time of wider international scrutiny of the Jewish state after its high-seas raid on a Gaza-bound aid convoy.

"[Israel] is a serious security concern for the region and the world at large," Ali Asghar Soltanieh told reporters, criticising "crimes against humanity in Gaza. This sort of violation of international law plus nuclear capability is very dangerous for the security of the whole world."

Israel, like India, Pakistan and North Korea, is outside the NPT. The Jewish state says it cannot discuss the issue as long as many of its neighbours remain hostile to its existence.

It has neither confirmed nor denied having nuclear weapons.