UN report reveals additional North Korea secret nuclear sites

The report relies on evidence from US scientist Siegfried Hecker who visited a secret site in November last year, where he told a UN's panel of experts that the centrifuges he saw were likely to have originated other hidden facilities

During his visit in November, N. Korean officials showed Hecker an apparently fully functional uranium enrichment plant at the Yongbyon complex.

The reports quote unnamed diplomats. The panel’s report, not yet published, was handed to the Security Council last week. The panel, which assesses the sanctions regime against Pyongyang, was originally asked to produce the report after Hecker briefed the Security Council on his visit.

Diplomats told Bloomberg that their report concluded that centrifuges and other equipment at the Yongbyon reactor had previously operated at one or more secret locations.

Another diplomat told Reuters: "There's no way they could have outfitted the centrifuge facility between 2009 and now without there being additional secret sites."

According to the diplomats - not identified because the report has not yet been published - Hecker had told the panel it was unlikely that the North could have manufactured all of the equipment.

He maintained, according to the diplomats, that it was more likely that they had imported some materials and assembled them in at least one secret location, before moving them to Yongbyon.

The panel's report recommends tightening sanctions to include asset freezes and travel bans on nuclear officials, according to leaks from diplomats. The report is expected to be made public later in the week.