Campaign group Amnesty International has documented what it believes to be an upgrade to a crematorium at one of the sites, along with new guard posts and enhanced security.
Images appear to show prisoners labouring on agricultural land within the camp.
North Korea refuses to admit the existence of the political prison camps, also known as “kwanliso” – where an estimated 120,000 people are believed to be held and hundreds of thousands are thought to have died over the past five decades, according to a UN report in 2014. – READ MORE
Satellite images reveal ‘industrial scale’ of North Korean prison camps
New satellite imagery of North Korea’s network of prison camps shows abuse is taking place “on an industrial scale”.