North Korea 'resumes work' on light water reactor

North Korea has resumed work on a light water reactor that could be used to support its nuclear programme after ''months of inactivity'', a United States institute says.

The analysis was based on satellite photographs taken on 30 April showing new construction at the Yongbyon site.

Pyongyang is ''now close to completion'' of the reactor containment building, the institute said.

But it may take one to two more years before the site is fully operational.

The reactor, which Pyongyang says is to meet energy needs, is a prototype for other, larger reactors already in the pipeline, says the BBC's Lucy Williamson in Seoul.

The ''next major step in construction'' following the completion of the building would be the loading of ''heavy components, such as the pressure vessel, steam generator and pressuriser'' through the roof, said the analysis published on the 38north website .

The institute at the Paul H. Nitze School of Advanced International Studies (SAIS) at Johns Hopkins University has been analysing satellite photographs of the experimental light water reactor since last year.

It tracked ''rapid progress'' in 2011 and found that work at the site stopped in late December.

''Exactly why the work stopped remains unclear,'' the institute said.

It could have been partly due to the death of North Korean leader Kim Jong-il in December, or more likely, the approach of winter, it added.

Pyongyang first revealed that it was building a new reactor in 2010 when it showed US scientists a uranium enrichment plant reportedly producing fuel for the new facility.

Officials said both the light water reactor and enrichment plant were meant to produce power for civilian use.

But experts said the reactor could be used to produce plutonium and the plant could be converted to produce highly enriched uranium for weapons.

News of progress on the reactor site comes amid reports that North Korea may be planning to carry out a third nuclear test.