North Korea, the reclusive state ruled by dictator Kim Jong Un, claims to have carried out a hydrogen bomb test early on Wednesday. +
If confirmed it would be the North's fourth nuclear test since 2006.
President Park Geun-hye of South Korea said she would ask her country's international allies to ensure the regime in Pyongyang was punished for carrying out the test.
However, an unnamed South Korean military official told Yonhap news agency that the explosion was 'too weak' to have been a hydrogen bomb. +
The UN Security Council unanimously condemned the test.