U.S. officials suspect it was a nuclear test that shook the ground in North Korea, not an earthquake as first thought.

FOX's Rachel Sutherland reports from Washington:

It will take time to verify the claim, but State Department spokesman John Kirby says the U.S. will respond appropriately to all North Korean provocations.

Republican Presidential front-runner Donald Trump is blaming China, telling "FOX & Friends":

(Trump) "They have total control over North Korea. And China should solve that problem. And if they don't solve the problem we should make trade very difficult for China."

GOP candidate Marco Rubio says the President has been standing idly by while North Korea expands its arsenal.

In Washington, Rachel Sutherland, FOX News.