H-bomb test "grave violation" of North Korea's obligations if true

North Korea's reported test of a hydrogen bomb would be a "grave violation" of the country's international obligation not to produce a nuclear weapon, the EU's foreign policy chief said on Wednesday.

"If confirmed, this action would represent a grave violation of (North Korea's) international obligations not to produce or test nuclear weapons, as determined by several United Nations Security Council Resolutions," Federica Mogherini said in a statement.

She said it would also be "a threat to the peace and security of the entire Northeast Asia region."