Boris Johnson has warned President Donald Trump that taking military action against North Korea could provoke Kim Jong-un to “vaporise” the South Korean population in response.

Pyongyang announced on Sunday that it had successfully tested a hydrogen bomb that could be loaded onto a long-range missile, which Mr Johnson described as “a new order of threat”.

The Foreign Secretary condemned Pyongyang’s “reckless” act, and said that “all options are on the table, but we really don’t see any easy military solution”.