Here are key dates in its missile programme:

Late 1970s: Starts working on a version of the Soviet Scud-B (range 300 kilometres or 186 miles). Test-fired in 1984

1987-92: Begins developing variant of Scud-C (500 km), Rodong-1 (1,300 km), Taepodong-1 (2,500 km), Musudan-1 (3,000 km) and Taepodong-2 (6,700 km)

Aug 1998: Test-fires Taepodong-1 over Japan as part of failed satellite launch

Sept 1999: Declares moratorium on long-range missile tests amid improving ties with US

July 12, 2000: Fifth round of US-North Korean missile talks ends without agreement after North demands $1 billion a year in return for halting missile exports

March 3, 2005: North ends moratorium on long-range missile testing, blames Bush administration’s “hostile” policy

July 5, 2006: North test-fires seven missiles, including a long-range Taepodong-2 which explodes after 40 seconds

Oct 9, 2006: North conducts underground nuclear test, its first

April 5, 2009: North Korea launches long-range rocket which flies over Japan and lands in the Pacific, in what it says is an attempt to put a satellite into orbit. The United States, Japan and South Korea see it as a disguised test of a Taepodong-2

May 25, 2009: North conducts its second underground nuclear test, several times more powerful than the first

April 13, 2012: North launches what it has said is a long-range rocket to put a satellite into orbit, but it disintegrates soon after blast-off and falls into the ocean

December 12, 2012: North launches a multi-stage rocket and successfully places an Earth observational satellite in orbit

February 12, 2013: Conducts its third underground nuclear test

January 6, 2016: North conducts its fourth underground nuclear test, which it says was of a hydrogen bomb — a claim doubted by most experts

February 7, 2016: North Korea launches a satellite-bearing rocket, an operation widely seen as a covert ballistic missile test

March 9, 2016: Kim Jong-Un claims the North has successfully miniaturised a thermo-nuclear warhead

April 15, 2016: North Korea tries but fails to test-fire what appears to be a medium-range missile on the birthday of founding leader Kim Il-Sung

April 23, 2016: North test-fires a submarine-launched ballistic missile

July 8, 2016: US and South Korea announce plans to deploy an advanced missile defence system — the US THAAD (Terminal High Altitude Area Defense)

August 3, 2016: North Korea fires a ballistic missile directly into Japanese-controlled waters for the first time

August 24, 2016: Successfully test-fires a submarine-launched ballistic missile, in what it says is retaliation for large-scale South Korea-US military exercises

September 5, 2016: North Korea fires three ballistic missiles off its east coast as top world leaders meet at the G20 summit in China

September 9, 2016: Fifth nuclear test

October 15, 2016: An intermediate-range Musudan missile, theoretically capable of reaching US bases on Guam, is tested but explodes shortly after launch

February 12, 2017: North conducts test of ballistic missile which flies about 500 kilometres (310 miles) before falling into the Sea of Japan

March 6, 2017: North fires four ballistic missiles in what is says is an exercise to hit US bases in Japan. Three come down in waters that are part of Japan’s exclusive economic zone

March 7, 2017: US begins deploying THAAD missile defence system in South Korea

March 19, 2017: North Korea says it has tested a new rocket engine

April 5, 2017: North Korea fires a ballistic missile into the Sea of Japan (East Sea), which the US says was an extended-range Scud missile

April 16, 2017: North Korea stages a failed missile test

April 29, 2017: North test-fires a ballistic missile which fails after a brief flight

May 2, 2017: THAAD anti-missile system goes operational in South Korea

May 14, 2017: North fires a ballistic missile which flies 700 kilometres before landing in the Sea of Japan.