North Korea suspected to have conducted fifth and largest nuclear test

North Korea says it has conducted a "nuclear warhead explosion" test meant to counter what Pyongyang calls U.S. hostility.

The 5.3 magnitude seismic event in North Korea on Friday, thought to have been the North's fifth nuclear test, would indicate a device with a 20- to 30-kilotonne yield, an analyst said, the largest yield estimate yet of a North Korean nuclear device.