Around 2.5 tons of natural uranium have gone missing from a Libyan site outside state control, UN nuclear watchdog cautioned in a statement Wednesday.

"The loss of knowledge about the present location of nuclear material may present a radiological risk, as well as nuclear security concerns," a statement by International Atomic Energy Agency (IAEA) chief Rafael Grossi said, adding that reaching the site required "complex logistics."

Reuters quotes Grossi as saying that the finding is the result of an inspection originally planned for last year that "had to be postponed because of the security situation in the region" and was finally carried out on Tuesday.

IAEA inspectors "found that ten drums containing approximately 2.5 tons of natural uranium in the form of UOC (uranium ore concentrate) previously declared by (Libya) ... as being stored at that location were not present at the location," the statement added.

The agency noted that it would take action to determine the circumstances of the uranium's removal from the site, which it did not name, and where it is now.

In late 2003 Libya under Muammar Gaddafi voluntarily rolled back its nuclear weapons programme, which included centrifuges that can enrich uranium as well as design information for a nuclear bomb, though it remained far from achieving this goal.