North Korea urged to halt nuclear testsListen /
The United Nations continues to monitor developments in the Democratic People's Republic of Korea (DPRK) following the country's testing of a nuclear bomb.
Dr Lassina Zerbo is at the helm of the Vienna-based CTBTO, the UN body which monitors nuclear explosions worldwide in line with the Comprehensive Nuclear-Test-Ban Treaty.
CTBTO monitoring stations had picked up "unusual" seismic activity in the DPRK on Wednesday morning, in the area of the country's nuclear test site.
Cristina Silveiro spoke with Dr Zerbo to find out more.