SEOUL, Sept. 3 (Yonhap) -- The following is a chronology of major events related North Korea's nuclear tests.
Oct. 9: North Korea says it successfully carried out its first test of a nuclear device.
Oct. 15: The U.N. Security Council votes unanimously to impose weapons and financial sanctions on North Korea over its nuclear test. Resolution 1718 demands Pyongyang eliminate all of its nuclear weapons, weapons of mass destruction and ballistic missiles.
Feb. 13: Pyongyang agrees to shut down its nuclear reactor and invites international inspectors within 60 days in return for massive energy assistance.
June 26-30: IAEA inspectors arrive in North Korea to discuss freezing its nuclear reactor, the first time they have been allowed into the country since 2002.
Sept. 2: Following bilateral talks in Geneva, the U.S. says North Korea has agreed to declare and dismantle all of its nuclear facilities by the end of the year.
June 27: North Korea explodes the cooling tower at its Yongbyon nuclear reactor, in a symbolic move to show its commitment to the talks on ending its nuclear program.
Aug. 26: Two months after submitting its nuclear declaration, Pyongyang says it has stopped disabling its nuclear facilities in protest of the delayed process to remove the country from the U.S. list of state sponsors of terrorism.
May 25: North Korea detonates an underground nuclear explosive device. This is North Korea's second nuclear test and is believed to be several times more powerful than the first one tested in 2006.
Nov. 12: Seigfried Hecker, a U.S. nuclear scientist, makes a visit to North Korea, where he is shown an advanced uranium enrichment plant in Yongbyon.
Nov. 30: North Korean state media says the construction of a light-water reactor and the production of low-enriched uranium are making progress.
Feb. 29: North Korea agrees to suspend uranium enrichment, as well as nuclear and long-range missile tests.
Jan. 24: North Korea's National Defense Commission says it will proceed with a "high-level nuclear test."
Feb. 4: North Korea's state media says its leader Kim Jong-un made an "important" decision regarding its security and sovereignty at a military meeting, amid mounting pressure on Pyongyang to scrap its plan for a nuclear test.
Feb. 12: North Korea conducts a third nuclear test at the Punggye-ri test site hours after the ruling Workers' Party Political Bureau vowed to continue to launch long-range rockets as part of an "all-out action of high intensity."
Jan. 6: North Korea conducts its fourth nuclear test in defiance of international condemnation. It claimed that it successfully conducted a hydrogen bomb test.
Sept. 9: North Korea carries out its fifth nuclear test on the 68th anniversary of the establishment of its regime. South Korea's defense ministry said that the yield of the blast is presumed to have been 10 kilotons, the largest ever conducted by Pyongyang.
Sept. 3: South Korea's weather agency detected a magnitude 5.7 earthquake from North Korea's nuclear test site in a sign of its sixth nuclear test. North Korea's official news agency Korean Central News Agency reported earlier in the day they have developed hydrogen bombs that can fit on the country's intercontinental ballistic missiles.
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