The United Nations Security Council will hold an emergency meeting later on Wednesday to discuss North Korea’s claims that it carried out a successful hydrogen bomb test that morning. The talks were called by Japan and the United States, reports said. North Korea has held nuclear tests before, in 2006, 2009 and 2013, after which it came in for a series of sanctions from the UN.

If North Korea’s claims are true, it marks a significant advance in its military capabilities and may likely trigger more sanctions for its banned nuclear programme. The Telegraph reported that South Korea has played down claims that it was a hydrogen bomb test, since the blast detonations did not indicate it was a very powerful bomb.