Officials have concealed the incident because Kim Jong Un wants crude oil and food aid from Russia, one source says.
Public executions are common, with gruesome methods frequently used, sources say.
They say the regime leader is exposing the country’s technology.
The move reflects worsening relations with China, source of many foreign movies, residents say.
Sources say Kim Jong Un ordered it closed to prevent news of the break out.
Hyon Yong Chol, accused of disloyalty to Kim Jong Un, was killed by anti-aircraft fire while hundreds watched on April 30.
They ask for strengthened units amid growing numbers of assaults by soldiers and civilians.
Most citizens believe the propaganda to be true, while those who have access to outside information know authorities are bluffing.
The 16 people fled the country during a “special monitoring period” for citizens.
Shortages in electricity and raw materials have held back production, sources say.