“Russian Military Structures Consider Version on TU-154 Shaking Down by Ukranian Missile as Faithless” (sic)
-Russia Today headline

“Ukraine's defence ministry has denied that its forces had caused the crash.

Ukrainian defence ministry
But a US official in Washington and a Ukrainian navy official in Kiev both said the accident might have been caused by a Ukrainian surface-to-air missile.

Ukrainian navy official Igor Larichev told the AFP news agency that the Ukrainian army had shot down the plane by mistake during a training exercise. ”

sidebar:

All the rockets used during the training exercise had guaranteed service lives and self-destruction mechanisms in case they deviated from their course
-BBC

Russian jet hit by missile: theory
CNN article
-CNN

There have apparently been accidental missile shootdowns of civilian airliners in the past, including an Air Lingus flight near England in the late 60's, and a more recent event over the Mediterranean. So far (to my knowledge), there has never been any official acknowledgement of any such accident ever occuring.

sp