LONDON - British Foreign Secretary Philip Hammond on Wednesday described North Korea's nuclear test as a "provocation" and a "grave" breach of United Nations Security Council resolutions.
Hammond wrote on Twitter: "If North Korean H-bomb test reports are true, it is a grave breach of UNSC (UN Security Council) resolutions and a provocation which I condemn without reservation" after Pyongyang claimed to have tested a hydrogen bomb.
The announcement, which met with scepticism among nuclear experts, sparked a flurry of international criticism and prompted the UN Security Council to call an emergency meeting.
The British foreign secretary, who is on an official visit to key North Korean ally China, said London and Beijing would coordinate their reaction to the test.
"I have discussed this matter today in Beijing with my Chinese counterpart, State Councillor Yang Jiechi, and we have agreed to work with other members of the UN Security Council towards a robust international response," Hammond said in a statement.
Hammond is due to speak with his Japanese and South Korean counterparts Wednesday and visit Tokyo for meetings later this week, the statement said.
China is a key diplomatic protector of Pyongyang, though relations have been strained in recent years, partly due to North Korea's continuance of its nuclear programme despite international opposition.