It said the test proved North Korea was capable of mounting a nuclear warhead on a medium-range ballistic missile, which it last tested on Monday when Obama and other world leaders were gathered in China for a G20 summit.
North Korea Saturday sought to justify its weapons programme as a defence against U.S. nuclear "blackmail" as world powers debated ways to punish Pyongyang for its fifth and most powerful atomic test.
"If previous tests were conducted with the objective of acquiring the nuclear bomb, the newest test shows that the North finally owns a real, weaponized nuclear bomb", Kim said.
Search for traces of radionuclide or radioactive materials like xenon has been launched by South Korea and the U.S. Saturday after North Korea confirmed it successfully carried out a fifth nuclear test, the South's military officials told Yonhap News Agency.
North Korea's boast of a technologically game-changing nuclear test defied both tough worldwide sanctions and long-standing diplomatic pressure to curb its nuclear ambitions.
The explosive yield of Friday's blast would have been 10 to 12 kilotons, or 70 to 80 percent of the force of the 15-kiloton atomic bomb the United States dropped on the Japanese city of Hiroshima in 1945, according to South Korea's weather agency.
President Park Geun-Hye said, "Kim Jong-Un's regime will only earn more sanctions and isolation.and such provocation will further accelerate its path to self-destruction".
American defense officials expressed concern Friday that the tests demonstrate a new level of sophistication, though nongovernment experts in the USA are still hungering for evidence or formal analyses of where North Korean technology and industrial capability stand.
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Pyongyang hailed Friday's test as taking the North to "a higher level" through enhanced warhead capabilities, while vowing to carry on with its nuclear development.
"To be clear, the United States does not, and never will, accept North Korea as a nuclear state".
The Security Council met at the request of Japan, South Korea and the United States to agree on a response, despite resistance from Pyongyang's sole ally China to calls for tougher measures.
"The US is exasperated by the strong military steps being taken by the DPRK in a phased way".
South Korea's Park said late on Friday that Kim was "mentally out of control", blind to all warnings from the world and neighbours as he sought to maintain power.
Meanwhile, US presidential candidate Donald Trump seized on the test as an opportunity to take a jab at opponent Hillary Clinton.
The yield from Friday's test, which sparked global shockwaves, was estimated at 10 kilotons - nearly twice as much as the one Pyongyang conducted only eight months ago. "We are monitoring and continuing to assess the situation in close coordination with our regional partners", an NSC statement said.
