North Korea claims it tested first hydrogen bomb - live
Earthquake monitors detect seismic activity near known nuclear test site, soon followed by confirmation of a nuclear test by Pyongyang - follow live updates
A North Korean newsreader speaks during a broadcast on North Korean KRT
North Korea said on Wednesday morning that it had carried out a "successful" hydrogen bomb test, a claim that - if true - massively raises fears over the hermit state's banned nuclear programme.
International condemnation was swift with neighbours South Korea and Japan decrying a gross violation of UN Security Council resolutions, while the White House said it was still studying the precise nature of the apparent test and vowed to "respond appropriately".
Philip Hammond, the Foreign Secretary, joined the chorus of warnings.