North Korea has begun dismantling facilities at its nuclear test site, according to a satellite survey conducted by American researchers.

Analysts at the 38 North website say commercial imagery taken last week reveals that several support buildings have been demolished, railroads have been removed and mining carts overturned.

Pyongyang has promised to dismantle the Punggye-ri test site under the gaze of journalists between May 23 and 25.

The underground facility has been the site of all six North Korean nuclear tests.

The destruction of the site has been offered as an example of the secretive regime's commitment to disarming ahead of a historic meeting between Donald Trump and Kim Jong-un next month.