Japanese Prime Minister Shinzo Abe has spoken with with US President Donald Trump by phone and said that in face of an "escalating" situation with North Korea that close co-operation between their countries and South Korea was needed.
North Korea said on Sunday it has developed a more advanced nuclear weapon that has "great destructive power" and leader Kim Jong Un inspected a hydrogen bomb that will be loaded on a new intercontinental ballistic missile.
Abe and Trump also agreed that pressure on North Korea must be raised, Abe told reporters after the conversation.
