North Korea has confirmed it conducted a "successful" hydrogen bomb test which is believed to have caused an earthquake near a known testing site in the isolated country.
The state-owned Korean Central Television broadcast an official statement confirming the nuclear test on Wednesday (local time).
In the statement, North Korea says it would continue to strengthen its nuclear program in order to protect itself against the hostile policies of the United States.
It said it will not give up its nuclear program as long as the United States maintained what it called "its stance of aggression".
North Korea also said it will act as a responsible nuclear state and vowed not to use its nuclear weapons unless its sovereignty was infringed.
It also said it will not transfer its nuclear capabilities to other parties.
Earlier, South Korea's meteorological agency said the earthquake near the testing site was "likely" to have been caused by North Korea conducting a nuclear test.
The United States Geological Survey (USGS) reported a 5.1 magnitude quake that South Korea said was 49km from the Punggye-ri site where the North has conducted nuclear tests in the past.
"We suspect a man-made earthquake and are analysing the scale and epicentre of the quake," a Korea Meteorological Administration official told Reuters by phone.
While the USGS put the depth of the earthquake at 10km, the South Korean agency said it was near the surface. The earthquake was detected just after 10am (Seoul time).
South Korea's presidential office convened an emergency security meeting while Japan's chief government spokesman said the earthquake was likely caused by a nuclear test.
The last North Korean nuclear test, in 2013, registered at 5.1 on the USGS scale.
North Korea is known to have conducted three nuclear tests and is under UN sanctions for its nuclear and missile programs.
North Korean leader Kim Jong-Un had announced in December that North Korea had a hydrogen bomb and suggested they were capable of launching it, a statement that was met with scepticism by multiple nations including South Korea.
3 News / Reuters