Factbox: North Korea's missile and nuclear tests

SEOUL (Reuters) - A Chinese envoy arrives in South Korea on Monday to discuss North Korea's increasingly defiant weapons programme as a U.S. Navy strike group heads to the region amid concerns Pyongyang may be readying a fresh nuclear test. The following is a timeline of North's Korea's nuclear and missile tests. Aug. 1998: North Korea fires a multistage, long-range missile called Taepodong-I over Japan into the Pacific Ocean. North Korea called it a satellite launch. July 2006: North Korea test-fires a Taepodong-2 missile, which the United States says failed after launch. Oct. 2006: North Korea conducts first nuclear test. April 2009: North Korea says it successfully launches three-stage Unha-2 rocket carrying satellite. Washington says it failed. May 2009: North Korea explodes a nuclear device underground. April 2012: A slightly modified Unha-3 rocket explodes just after take-off. The North concedes failure. Dec. 2012: North Korea again launches a Unha-3 rocket, saying it successfully put a satellite into orbit. U.S. officials confirm an object in orbit, but no signal is detected. Feb. 2013: North Korea carries out third nuclear test. Jan. 6, 2016: North Korea says it successfully tests a hydrogen bomb. April 15, 2016: North Korea attempts to launch a Musudan missile but fails. Feb. 7, 2016: North Korea launches a long-range rocket, which it says put a satellite into orbit June 22, 2016: North Korea conducts two tests of an intermediate range Musudan missile after four failed launches of the same kind. July 18, 2016: North Korea fires three ballistic missiles off its east coast with a 500 km-600 km range. Aug. 3, 2016: North Korea fires two missiles, one of them landing in Japan's economic exclusion zone. Aug. 24, 2016: North Korea launches ballistic missile from a submarine, which flies 500 km. Sept. 5, 2016: North Korea fires three ballistic missiles about 1,000 kms (620 miles), one of which enters Japan’s air defence zone Sept. 9, 2016: North Korea conducts fifth nuclear test Sept. 20, 2016: North Korea says it complete ground test of a new rocket engine, which South Korea says is likely to be used for a long-range missile. Feb. 12, 2017: North Korea fires intermediate-range Pukguksong-2 ballistic missile into nearby seas. March 6, 2017: North Korea fires four ballistic missiles, three of them falling into Japan’s exclusive economic zone. March 19, 2017: North Korea announces rocket engine test, saying it will help country achieve “world-class satellite launch capability” March 22, 2017: A North Korean missile appears to explode just after launch. April 5, 2017: North Korea fires ballistic missile into the sea off its east coast. U.S. officials say it appears to be a liquid-fueled, extended-range Scud missile. (Reporting by Ju-min Park; Editing by Bill Tarrant and Lincoln Feast)