Seoul vows to punish Pyongyang for H-bomb test

South Korean vowed on Wednesday to forge a united stance with the international community to punish Pyongyang for going ahead with a fourth nuclear test.

Seoul will ensure that North Korea will pay the price for testing a hydrogen bomb, calling it a grave provocation and challenge to international peace and stability, President Park Geun-hye said.

"Now, the government should closely cooperate with the international community to make sure that North Korea pays the corresponding price for the nuclear test," Park said in a National Security Council meeting.

Park said it was important to induce the international community to impose strong sanctions on North Korea.

The comments came about two hours after North Korea announced that it has successfully conducted a hydrogen bomb test.

The North's nuclear test could prompt the UN Security Council to tighten its sanctions against North Korea. The communist country has already been under UN sanctions for its previous nuclear tests in 2006, 2009 and 2013.

Last year, Park warned that there will certainly be consequences if North Korea goes ahead with provocative actions that violate the UN Security Council resolutions.

South Korea on Wednesday issued a statement condemning North Korea for testing a hydrogen bomb and pledging to take all necessary measures against North Korea.

Park called on the military to maintain readiness in cooperation with the US troops in South Korea as she warned of a stern retaliation if Pyongyang stages a provocation against Seoul.

The US government said it could not confirm that North Korea had conducted a hydrogen bomb test, while vowing to respond appropriately to any "provocation".

"While we cannot confirm these claims at this time, we condemn any violation of UNSC (United Nations Security Council) resolutions and again call on North Korea to abide by its international obligations and commitments," White House National Security Council's spokesman Ned Price said.

The statement was in response to North Korea's announcement that it had successfully carried out its first hydrogen bomb test.

Price added that the US would continue to protect and defend its allies in the region, and "respond appropriately to any and all North Korean provocations".

Meanwhile, Japan has also condemned the hydrogen bomb test conducted by North Korea, saying the test was a "significant threat".

"The hydrogen bomb test is a significant threat to Japan's national security and is unacceptable," Japanese Prime Minister Shinzo Abe said.

Japan will consider sanctions against North Korea as its nuclear test violates UN Security Council's relevant resolutions, Abe said.

Abe also said Japan will work with the US, South Korea, China and Russia to cope with the issue.

Japanese Foreign Minister Fumio Kishida will hold talks with the US Ambassador Caroline Kennedy over the nuclear test.