A satellite image of the Yongbyon nuclear complex.

Construction of North Korea's latest nuclear facility has passed a major milestone, with a dome now in place atop the new light-water reactor in Yongbyon.

Satellite images clearly show the 21-metre diameter dome emplaced over the main structure.

Allison Puccioni, an analyst with Jane's Defence Weekly, described the dome as "a major step in [North Korea's] mission to build a modern, indigenous nuclear reactor". However, it is thought that the light-water facility is still some way from completion.

North Korea says the reactor will be used to generating electricity. However, many experts doubt whether this is the true motive.

North Korea has tested two nuclear bombs since 2006, and it is widely believed that the reactor could be used to produce uranium or plutonium for nuclear weapons.

The Yongbyon compound has previously housed a plutonium-producing facility, which was demolished in 2007 as part of an international disarmament deal. However North Korea has subsequently abandoned this compact.