North Korea has carried out its fifth nuclear test since it began its quest for nuclear arms in 2006, causing fresh concerns for its neighbours.
A list follows of the most significant North Korean tests in the past decade, and the international response:
October 9, 2006: North Korea carries out its first atomic test.
October 14, 2006: The UN Security Council unanimously imposes commercial sanctions and bans North Korea from importing ballistic missile technology in response to its nuclear test.
April 5, 2009: North Korea launches a Unha-2 rocket and says it placed a satellite into orbit, but outside experts say no satellite can be detected.
May 25, 2009: North Korea conducts its second atomic test.
June 12, 2009: The UN Security Council unanimously adopts stricter sanctions, including the interception of North Korean ships.
April 13, 2012: North Korea launches a long-range Unha-3 rocket, which explodes minutes after takeoff.
December 12, 2012: North Korea says a launch of another Unha-3 rocket was successful and it placed a satellite into orbit.
January 22, 2013: The UN Security Council condemns the latest launch and extends asset freezes and travel bans to several North Korean organizations and individuals.
February 12, 2013: North Korea appears to carry out its third atomic test, according to seismic data. Pyongyang claims it used a miniaturized nuclear device, but no radiation was detected.
March 7, 2013: New UN sanctions target "illicit activities of diplomatic personnel, transfers of bulk cash, and the country's banking relationships."
September 15, 2015: North Korea says it has restarted operations of the nuclear reactor at its Yongbyon facility after making "innovations" at the complex.
January 6, 2016: North Korea claims it has successfully tested a hydrogen bomb, its fourth test of an atomic device, but Western experts doubt it had the power of a hydrogen nuclear explosion.
February 7, 2016: North Korea launches a long-range rocket and puts Earth observation satellite Kwangmyongsong-4 into orbit, although US reports said it was not operating correctly. The rocket launch is seen as a test of nuclear-capable weaponry.
March 2, 2016: UN imposes toughest sanctions yet on Pyongyang, including a complete ban on the sale of all conventional weapons and inspections of all North Korean cargo. In response to the sanctions and to US-South Korea joint military exercises, Pyongyang threatens nuclear war and fires a series of ballistic missiles.
March 24, 2016: The regime says it has successfully tested a solid-fuel rocket engine, which observers say could make missile launches easier and more frequent.
April 5, 2016: China, historically Pyongyang's only significant international ally, restricts its trade with North Korea.
April 9, 2016: North Korean leader Kim Jong Un announces that recent tests of an improved jet engine were successful, improving the range of Pyongyang's intercontinental ballistic missile nuclear deterrent.
May 31, 2016: North Korea again attempts to fire a Musudan missile, the latest in a series of unsuccessful launches since April.
June 23, 2016: North Korea claims to have launched an intermediate-range ballistic missile in what it calls a "simulated strike on South Korea."
September 5, 2016: North Korea test fires three ballistic missiles to coincide with a G20 meeting in Hangzhou, China.
September 6, 2016: The UN Security Council "strongly condemns" the North Korean missile launch.
September 9: Japan confirms that North Korea has carried out a fifth nuclear test and says it will "lodge a strong protest."