The UN Security Council is planning to hold an emergency meeting on Wednesday to discuss North Korea's reported test of a hydrogen bomb, the US mission to the United Nations said.

Speaking to Reuters on condition of anonymity, several diplomats said the meeting was scheduled to take place at 11 am ET (1600 GMT). The diplomats said the meeting would likely be held behind closed doors.

"The United States and Japan have requested emergency Security Council consultations for tomorrow morning regarding North Korea's alleged nuclear test," Hagar Chemali, spokeswoman for the US mission, said in a statement.

"While we cannot confirm at this time that a test was carried out, we condemn any violation of UNSC (UN Security Council) Resolutions and again call on North Korea to abide by its international obligations and commitments," she added.

North Korea said it had successfully conducted a test of a miniaturised hydrogen nuclear device on Wednesday morning, marking a significant advance in the isolated state's strike capabilities and raising alarm bells in Japan and South Korea.

It was not immediately clear what action, if any, the 15-nation council was planning to take in response to the North Korean statement that it had conducted a fourth nuclear test.

Pyongyang has been under UN Security Council sanctions due to its nuclear weapons program since it first tested an atomic device in 2006.

One Western diplomat said that if the latest North Korean nuclear test was confirmed, council members would seek to expand existing UN sanctions against Pyongyang.  -Reuters