Updated

The latest on the North Korean announcement it has conducted a hydrogen bomb test (all times local):

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1:25 p.m.

The U.N. organization monitoring the world for signs of nuclear testing says it has detected "an unusual event in the Korean Peninsula."

The head of the Comprehensive Test Ban Treaty Organization Lassina Zerbo says in a statement: "Our International Monitoring System detected an unusual seismic event in the Korean Peninsula at latitude 41.27 longitude 129.10."

The location on the map places the epicenter at North Korea's Pyunggye-ri testing site in its northeastern mountains, where all of its nuclear tests have been conducted.

North Korea said Wednesday it had conducted a hydrogen bomb test, which, if confirmed, would put Pyongyang a big step closer toward improving its still-limited nuclear arsenal.

— George Jahn, Vienna