Several countries, including the US, China, Russia and Japan, have condemned North Korea's fifth nuclear test.
Pyongyang said on Friday it has successfully conducted a test of a nuclear warhead on the day of the 68th anniversary of its national foundation.
The regime can now mount a warhead to a strategic ballistic missile, state media said, making its attacking range much greater.
Earlier, a seismic event with a magnitude of 5.3 was detected in an area near the country's key nuclear test site in its northeast at 9am Pyongyang time.
The UN Security Council will convene an emergency meeting Friday afternoon, possibly to issue a statement addressing North Korea's fifth nuclear test, diplomatic sources said.
The move by the powerful 15-member council came in response to requests for such a meeting from Japan, the United States and South Korea, the sources said.
The Security Council is likely to release a statement strongly condemning Pyongyang for detonating a nuclear device in defiance of past UN resolutions on the isolated country.
The council is also likely to encourage all UN member states to implement the sanctions imposed on North Korea in March while possibly contemplating further measures.
The council, which has adopted a resolution imposing additional sanctions every time Pyongyang conducts a nuclear test, is expected to do so this time, too.
In March, North Korea was subject to the harshest round of sanctions ever after it carried out its fourth underground nuclear test in January and launched a rocket using ballistic missile technology the following month.
The new sanctions expanded freight inspection to cover all cargo to and from North Korea, not just those ships suspected of transporting illicit goods, and tightens existing measures curbing the presence and operations of North Korean banks outside the country.
Even if the council decides to adopt a fresh sanctions resolution on North Korea this time, it is likely to complement the March resolution at best.
The head of the International Atomic Energy Agency says the test, if confirmed, is in clear violation of numerous UN Security Council resolutions and in complete disregard of the repeated demands of the international community.
Yukiya Amano says in a statement that the test is a "deeply troubling and regrettable act".
The Comprehensive Nuclear-Test-Ban Treaty Organization also says that the test, if confirmed, "constitutes yet another breach of the universally accepted norm against nuclear testing; a norm that has been respected by 183 countries since 1996."
The agency's executive secretary, Lassina Zerbo, says in a statement that Friday's detonation seems to have been slightly larger than the one recorded on Jan 6.
Strong criticisms
While China criticised the test, observers view Beijing is unlikely to follow up with strong action because its influence is limited and it believes the US and South Korea share responsibility for growing tensions in the region.
China, Pyongyang's main diplomatic ally, is key in any effort to rein in North Korea's nuclear programme. But it has been infuriated by the isolated nation's nuclear and missile tests and has signed up to increasingly tough United Nations sanctions.
Foreign ministry spokeswoman Hua Chunying said China would lodge a diplomatic protest with North Korea at its embassy in Beijing for conducting the test.
China's official Xinhua news agency, in a commentary after North Korea confirmed the test, said it was shocking and unwise and would only "add oil to the flames".
But it added that nobody benefited from chaos or war in Korea and all parties in the international community should exercise restraint and avoid doing anything that is "mutually irritating".
"Not long along, South Korea ignored the strong opposition of neighbouring countries and decided to deploy the THAAD system, which is diametrically opposed to efforts to maintain peace and stability on the peninsula, has seriously damaged regional strategic balance and caused a rise in tensions on the peninsula."
Meanwhile, Japanese Prime Minister Shinzo Abe, described the programme as a “grave threat” to Japan.
South Korean President Park Geun-hye denounced the test as a clear violation of security council resolutions banning the North from developing nuclear and other weapons of mass destruction. Park accused Kim of “maniacal recklessness” in his pursuit of building a viable nuclear arsenal, according to her office.
Russian foreign minister Lavrov said in Geneva Russis was "very much concerned" about North korea, strong message must be sent on implementing security council resolution
France became the latest to join the chorus of world leaders condemning the move.
France's Foreign Minister Jean-Marc Ayrault said the international community "must unite against this new provocation".
He added Friday's test is a "serious act which infringes the world's peace and security....this escalation is unacceptable."
Norwegian Foreign Minister Borge Brende also condemned Pyongyang's nuclear test, saying in a tweet that "this unacceptable action causes deep concern and threatens peace".