North Korea has claimed to have successfully tested a hydrogen bomb, which if confirmed will bolster the country's nuclear strike capabilities.
Reports emerged that the testing triggered seismic activity of 5.1 on the Richter scale 49km away from the Punggye-ri site in the North Hamgyong province.
A report on state TV said North Korea had launched a "miniaturised" hydrogen bomb, and that the test was a "perfect success."
UN spokeswoman Hagar Chemali was quoted by AP as saying: "While we cannot confirm at this time that a test was carried out, we condemn any violation of UNSC Resolutions and again call on North Korea to abide by its international obligations and commitments."
Both the US and South Korea could not confirm whether North Korea's test was a success.
Additionally, South Korean media reports said that North Korea had conducted an ejection test of its new Bukkeukseong-1 (Polaris-1, KN-11) submarine-launched ballistic missile (SLBM) as a part of its SLBM development programme, at the Sinpo South Shipyard.
The test follows an earlier failed launch test in 28 November 2015, in the waters of the East Sea, northeast of Wonsan.
The recent test is believed to have been performed as an underwater test platform.
According to Bruce Bechtol, a former Defense Intelligence Agency expert on North Korea, the missile used in the test could be a variant of an SS-N-6 SLBM procured from Russia, which had been refurbished and remodelled.