The investigation into the assassination of former State Duma deputy Denis Voronenkov is probing into two theories, i.e. his murder as a witness to the former Ukrainian President Viktor Yanukovych case and as a witness to contraband in the Federal Security Service (FSB) structure, Ukrainian Prosecutor General Yuriy Lutsenko said.

"At the time preliminary theories are a theory of his assassination as a witness to the Yanukovych case, and the murder within the FSB contraband case covered by the president of the Russian Federation," he told a news briefing in Kyiv on Thursday.