The UN nuclear watchdog said on Tuesday information stolen from one of its former servers had been posted on a hacker site this week, and that it was taking "all possible steps" to ensure its computer systems were protected.

The International Atomic Energy Agency, which is investigating Iran's nuclear activity, said the information concerned contact details of experts working with the IAEA but it did not say who might have been behind the action.

It alluded to a statement posted on a website which called for an investigation into Israel's nuclear activities - a demand often voiced by Iran and Arab states.

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

Measures had already 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.