How does a Buk missile system work?

International prosecutors investigating the downing of flight MH17 over eastern Ukraine in 2014 say the missile that hit the plane was fired from territory controlled by Russian-backed rebels.

They said the missile launcher was brought into Ukraine from Russia.

A previous report by the Dutch Safety Board found that the weapon used was a Buk surface-to-air missile system.

The Ukrainian military has given BBC News access to one of its Buks, to show how sophisticated a piece of military equipment it is.