Uranium ore concentrate is considered to emit low levels of radioactivity.

IAEA inspectors on Tuesday found that “10 drums containing approximately 2.5 tonnes of natural uranium in the form of uranium ore concentrate … were not present” as previously declared at the location, it said.

The substance is commonly known as “yellowcake”, a powder consisting of around 80 per cent uranium oxide. It is used in the preparation of nuclear fuel for reactors and can also be enriched for use in nuclear weapons.

The site “is currently not under the regulatory control of Libya’s state authority”, the report said, without identifying the site or saying why Libya was in possession of the material.

The North African country remains split between a nominally interim government in the capital Tripoli in the west, and another in the east backed by Haftar.

Mahjoub published a video showing a man in a protective suit counting 18 blue containers, the total that had been stored at the site.

“The situation is under control. The IAEA has been informed,” Mahjoub told Agence France-Presse.

He suggested the containers had been stolen and then abandoned by “a Chadian faction who thought they were weapons or ammunition”.

Profiting from Libya’s years of chaos and porous borders in the desert region, fighters from neighbouring Chad and Sudan established rear bases in Libya’s south.

An inspection of the site had initially been scheduled for 2022 but had to be postponed because of the “security situation in the region”, the IAEA report said.

It said the location was routinely monitored by the IAEA through commercial satellite imagery and other open-source information.

It was through analysing these images that the agency decided to make a physical inspection, despite the security risk and logistical challenge, it said.

On Facebook, Mahjoub said that after the inspection revealed the disappearance, Haftar-linked forces recovered the containers.

Libya under Gaddafi had a suspected nuclear weapons programme, which it scrapped in 2003.