Seoul:
North Korea, which admitted the failure of its long-range rocket launch on Friday, has been developing missiles for decades both for what it terms self-defence and as a lucrative export commodity.
It had said that the launch was to put a satellite in orbit to collect data on forests and natural resources within its territory.
The United States and its allies swiftly condemned what they claimed was a disguised test of ballistic missile technology in defiance of UN resolutions.
The North began its programme in the late 1970s or early 1980s, when it started working on a version of the Soviet Scud-B with a range of 300 kilometres (around 185 miles).
Between 1987 and 1992 it began developing a variant of the Scud-C (range 500 kilometres), as well as the Rodong-1 (1300 kilometres), the Taepodong-1 (2500 kilometres), the Musudan-1 (3000 kilometres) and the Taepodong-2 (6700 kilometres).
The Scud-B, Scud-C and Rodong-1 have all been tested successfully.
The first and only Taepodong-1 launch took place in August 1998 over Japan. It sparked alarm in Tokyo but the third stage apparently exploded before it could place a small satellite into orbit.
In September 1999, amid improving relations with the United States, North Korea declared a moratorium on long-range missile testing which it ended in March 2005, blaming Washington's "hostile" policy.
The Taepodong-2 was first fired on July 5, 2006 but blew up after 40 seconds.
On April 5, 2009, the North fired a long-range rocket dubbed Unha-2 (Galaxy-2) -- an advanced three-stage variant of the Taepodong-2 -- to put a satellite into orbit.
Experts said that the third stage may have separated from the second but apparently failed to ignite.
Japanese reports said that the second stage splashed down in the Pacific 3200 kilometres from the launch site, and the third stage plus satellite fell nearby.
Unha-2 is 30 metres (100 feet) tall and weighs 80-85 tonnes, according to a 2009 analysis by scientists David Wright and Theodore Postol.
Writing in the Bulletin of the Atomic Scientists, they termed it a "significant advance" on previous launchers and said a modified version could reach the continental United States.
They said that the third stage had a strong similarity to Iran's Safir-2 rocket, suggesting collaboration between the two countries.
The Unha-3 rocket, which the North said was to put the Kwangmyongsong-3 satellite into orbit, exploded shortly after its launch on Friday from a newly built space centre in the northwest of the country, splashing down in the Yellow Sea off South Korea.
South Korea said it was watching for further missile tests or a third nuclear test following the rocket failure.
The North is thought to have enough plutonium for six to eight small bombs. But it is unclear whether it has mastered the technology to build a nuclear warhead.
It is thought to have sold hundreds of ballistic missiles to Iran, Iraq, Syria, Pakistan and other countries over the previous decade to earn foreign currency, according to a US Congressional Research Service report in 2007.
Leaving aside the longest-range missiles, the main security threat is seen as coming from around 800 road-mobile missiles.
Of these, about 600 are Scuds capable of hitting targets in South Korea, and possibly Japanese territory in some cases. There are another 200 Rodong-1 missiles that could reach Tokyo.