TOKYO Japan and Britain said on Friday the international community should respond firmly and swiftly after North Korea's announcement that it had successfully tested a hydrogen nuclear device.
After a meeting of the Japanese and British foreign and defence ministers, the two countries also said they would hold joint exercises and cooperate on defence equipment.
"We've agreed that North Korea's nuclear test poses grave threats to peace and the safety of international society and that the international community needs to take resolute steps quickly," Japanese Foreign Minister Fumio Kishida said.
British Defence Secretary Michael Fallon said: "We will be deepening our bilateral defence cooperation ... bringing our own forces closer together to more regular exercises and exchanges."
Fallon said Japan and Britain had agreed to move to a higher level of feasibility study on an air-to-air missile system they are planning to develop.
The meeting comes as Japanese Prime Minister Shinzo Abe aims to bolster Tokyo's role on the global security stage and after North Korea's announcement on Wednesday that it had tested a miniaturised hydrogen nuclear bomb, drawing threats of further sanctions on the isolated nation.
British Foreign Secretary Philip Hammond told reporters: "Our relationship is underpinned by a growing defence and security partnership, reflecting our shared ambition to contribute not only to global prosperity but also to global peace and security."
Hammond earlier urged South Korea to show restraint after Seoul resumed propaganda broadcasts following the North's announcement.
(Reporting by Kiyoshi Takenaka; Editing by Janet Lawrence)