The Malaysian Airlines flight MH-17 is believed to have been shot down by an advanced Russian built surface-to-air missile system called the 9K37 BUK.
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The BUK is a family of medium range, surface-to-air systems developed by the Soviet Union in the Cold War era.
The BUK system can strike targets at heights upto 72,000 feet. The Malaysian jet was flying at 33,000 feet.
A message on the official Twitter account of the Donetsk People's Republic had announced hours earlier that insurgents had seized a series of Russian-made Buk systems capable of soaring to that height. That tweet was later deleted.
According to a Ukrainian state-owned firm, the country's military operates the Buk-M1 system designed to shoot down military aircraft, including helicopters, as well as cruise missiles.
The BUK system has been constantly upgraded over the years and uses very advanced missiles.
Each mobile BUK system has a launch vehicle, a radar vehicle and a command complex.
Each BUK hold four missiles mounted on top of a vehicle so they can be transported quickly.
The missile uses a radar to find its target. Once it is fired, it can reach target at a height of 30 km, 3 times the height at which the flight was cruising.
Each missile carries a 70 kg explosive tip which explodes when it is closest to the target. Then the warhead showers shrapnel.
Experts have said that both Ukrainian and Russian forces operate the BUK system which fires the very advanced SA-17 surface to air missile.