VIENNA - The UN nuclear agency chief said on Thursday a hacking incident involving one of its servers was "deeply regrettable" but suggested that no sensitive information related to Iran's atomic activities had been stolen.

Yukiya Amano said the hacking - first reported by the International Atomic Energy Agency on Tuesday - had happened several months ago and that the server concerned had been closed down.

The hackers - a group using an Iranian-sounding name - on Sunday posted email addresses of experts who have been working with the United Nations on a website, and urged the IAEA to investigate Israel's nuclear work.

"We don't know everything (about the incident) but we are confident that safeguards information has not been stolen," Amano told a news conference.

"Safeguards" means activities carried out by IAEA inspectors in investigating countries' nuclear activities, including Iran's, to make sure that no atomic material is diverted for weapons purposes.

The statement dated November 25 and headlined "Parastoo Hacks IAEA" said: "Israel owns a practical nuclear arsenal, tied to a growing military body."

Israel is widely believed to have the Middle East's only atomic arsenal but neither confirms nor denies this under a "strategic ambiguity" policy to deter Arab and Iranian foes.

The country is outside the Non-Proliferation Treaty that would require it to forswear nuclear weapons and open up its reactor in the southern desert town of Dimona.

Israel and the United States accuse Iran of seeking to develop a nuclear weapons capability, a charge Tehran denies, and says the Islamic state is the main proliferation threat.

Click here for full Jpost coverage of the Iranian threat

Iran and Arab states say Israel's assumed atomic arsenal threatens peace and security in the Middle East.

IAEA spokeswoman Gill Tudor said the agency "deeply regrets this publication of information stolen from an old server that was shut down some time ago."

Measures had been taken to address concern over possible vulnerability in the server, she said.

"The IAEA's technical and security teams are continuing to analyze the situation and do everything possible to help ensure that no further information is vulnerable," Tudor said.

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