BBC: North Korea has carried out its third, most powerful nuclear test despite UN warnings, and said "even stronger" action might follow.
It described the test as a "self-defensive measure" necessitated by the "continued hostility" of the US.
Its main ally, China, criticised the test, which was condemned worldwide.
Nuclear test monitors in Vienna say the underground explosion had double the force of the 2009 test, despite reportedly involving a smaller device.
If, as North Korea reports, a...