The UN atomic agency said Wednesday that hackers had accessed one of its computer servers and posted the contact details of some of the watchdog's experts online.

International Atomic Energy Agency spokeswoman Gill Tudor said "some contact details" related to experts working with the IAEA were published Sunday on a hacker site.

The hackers posted a statement on Cryptome.org calling for an investigation into the nuclear programme of Israel, the Middle East's sole if undeclared nuclear-armed country, which is not a signatory to the nuclear Non-Proliferation Treaty.

"The IAEA deeply regrets this publication of information stolen from an old server that was shut down some time ago. In fact, measures had already been taken to address concern over possible vulnerability in this server," Tudor said.

She added that the IAEA's technical and security teams "are continuing to analyse the situation and do everything possible to help ensure that no further information is vulnerable."