N. Korea conducts 3rd nuclear test, warns more ‘measures’ may come

This GeoEye Satellite Image captured January 23, 2013 shows the Punggye-ri nuclear test facility in North Korea. South Korea has detected an "artificial earthquake" in North Korea, Yonhap news agency reported on February 12, 2013, suggesting Pyongyang may have gone ahead with an expected nuclear test. (AFP Photo)

Pyongyang said the Tuesday morning explosion was part of an effort to protect its national security and sovereignty, citing US opposition to the recent North Korean space launch.

"It was confirmed that the nuclear test – that was carried out at a high level in a safe and perfect manner using a miniaturized and lighter nuclear device with greater explosive force than previously – did not pose any negative impact on the surrounding ecological environment," North Korea's KCNA state news agency said.

The UNSC has condemned the test by North Korea, calling it a “great violation of Security Council resolutions,” which poses “continuously a clear threat to international peace and security.”

The UN Security Council has unanimously approved the non-binding statement. The 15-member council "will begin work immediately on appropriate measures".

An hour after the test, Japan said that it is considering leveling further sanctions against North Korea.

"I have ordered that we consider every possible way to address this issue, including our own sanctions, while cooperating with other countries," Japanese Prime Minister Shinzo Abe told reporters after a meeting of Japan's security council.