Activity has been detected at a North Korean long-range rocket site suggesting Pyongyang may be pursuing the "rapid rebuilding" of a test facility after the collapse of the Hanoi summit, according to analysis of satellite imagery from a US think tank.

The Washington-based Centre for Strategic and International Studies (CSIS) says activity is "evident" at the vertical engine test stand and the launch pad's rail-mounted rocket transfer structure at the Sohae Satellite Launching Station — the facility from which Pyongyang launched satellites in 2012 and 2016. Sohae is also the site Pyongyang used as a test stand to fire some of its rocket engines on the ground. The satellite launches were condemned by the international community and widely viewed as disguised ballistic missile tests.