It is reported in United States Assessment of the Downing of Flight MH17 and its Aftermath.
"Over the past month, we have detected an increasing amount of heavy weaponry to separatist fighters crossing the border from Russia into Ukraine. Last weekend, Russia sent a convoy of military equipment with up to 150 vehicles including tanks, armored personnel carriers, artillery, and multiple rocket launchers to the separatist. We also have information indicating that Russia is providing training to separatist fighters at a facility in southwest Russia, and this effort included training on air defense systems", indicated in the statement.
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"Pro-Russian separatist fighters have demonstrated proficiency with surface-to-air missile systems and have downed more than a dozen aircraft over the past few months, including two large transport aircraft," mentioned in the statement.
At the time that flight MH17 dropped out of contact, we detected a surface-to-air missile (SAM) launch from a separatist-controlled area in southeastern Ukraine. We believe this missile was an SA-11.
Social media postings on Thursday show an SA-11 system traveling through the separatist-controlled towns of Torez and Snizhne, near the crash site and assessed location of the SAM launch.
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"Ukraine also operates SA-11 systems, but we are confident no Ukrainian air defense systems were within range of the crash. Ukrainian forces have also not fired a single surface-to-air missile during the conflict, despite often complaining about violations of their airspace by Russian military aircraft," claimed in the document.
Shortly after the crash, separatists claimed responsibility for shooting down a military transport plane on social media. Soon the separatists deleted social media posts boasting about shooting down a plane and possessing a Buk (SA-11) SAM system.
Audio data provided to the press by the Ukrainian security service was evaluated by Intelligence Community analysts who confirmed these were authentic conversations between known separatist leaders, based on comparing the Ukraine-released internet audio to recordings of known separatists.