Japan and China on Sunday strongly condemned North Korea's sixth nuclear test.
Japanese Prime Minister Shinzo Abe slammed the test, saying the country's "nuclear and missile development poses a grave and immediate new level of threat" and "seriously undermines peace and security of the region", Xinhua news agency reported.
"The UN Security Council has strongly criticized North Korea for repeatedly going ahead with ballistic missile launches this year... We find it completely intolerable that North Korea has conducted a nuclear test in such an environment," Abe said in the statement.
Meanwhile, Chinese Foreign Ministry issued a statement expressing firm opposition to and strong condemnation of the nuclear test by North Korea.
"North Korea has ignored the international community's widespread opposition and conducted a nuclear test again. The Chinese government expresses resolute objection to and strong condemnation of it," the ministry's statement said.
"We strongly urge North Korea to face the firm determination of the international community on the denuclearisation of the Korean Peninsula, fully abide by the relevant treaties of the UN Security Council... and return to the track of solving problems through dialogue," the statement added.
US National Security Adviser H.R. McMaster spoke with his South Korean counterpart, Chung Eui-yong, for about 20 minutes in an emergency phone call about the nuclear test, to discuss the possibility of deploying US military defence devices in South Korea.
Chung said South Korea will also seek new UN Security Council sanctions to "completely isolate" North Korea.
North Korea on Sunday said that in what could be the most powerful detonation so far, it successfully conducted a test of a hydrogen bomb that can be loaded onto a intercontinental ballistic missile (ICBM), state-media media reported.