The world is condemning North Korea's third nuclear test in defiance of a United Nations resolution banning the activity.
In South Korea, protesters turned out in the capital Wednesday to denounce the test and call for greater sanctions on the already impoverished North.
SOUNDBITE) (Korean) ANTI-NORTH KOREA PROTESTER CHOO SEON-HEE SAYING:
"The South Korean government and international society must punish North Korea strongly. A tough punishment is the only way to break the North."
Even China, the North's only regionally ally, expressed concern over the underground test.
This professor of international relations said North Korea's actions have only isolated the nation further and made it difficult for China, who opposes the country's nuclear testing, to support its ally.
It has also ratcheted up tensions in the region.
A spokesperson for the South Korean Defence Ministry said it has deployed cruise missiles that are ready to counter any attack immediately should authorities give the order.
But international condemnation has not cowed North Koreans -- far from it.
This women says no nation can stop North Korea from moving forward and making its own decisions.
North Korea said the test had "greater explosive force" than those it conducted in 2006 and 2009, indicating the element plutonium may have been used, which is also found in missile warheads.
World denounces North Korea nuclear test (1:33)
Feb. 13 - Nations condemn third North Korean nuclear test, including ally China. Jessica Gray reports. ( Transcript )