Interesting question.
IMHO it depends, how the device is exploding.
Subsurface: definitely.
Surface: yes
Midair: maybe not
Oceanic: yes
The Test in ROK were noticeable, but they caused a massive Avalanche and a Mountain nearly to collapse, they tested subsurface.
There are lot of people around in India and Pakistan who have iPhones and so on. It's nearly impossible, to make a possible Impact secret, or to hide that in case. On the other Hand, a Pakistani launch might be shot down by India. Pak was definitely launching Fateh Missiles and no one knows, what Payload they had :/