Ukraine's Prosecutor General Yuriy Lutsenko has said that the murder of former State Duma member Denis Voronenkov was ordered by a criminal boss controlled by the Russian Federal Security Bureau (FSB), Vladimir Tyurin, who is also the former common-law partner of Voronenkov's widow Maria Maksakova.

"The actual mastermind behind the murder, according to the Main Intelligence Department of the Defense Ministry of Ukraine confirmed by investigators of the capital city prosecutor's office is a criminal lord controlled by the FSB - Vladimir Anatolyevich Tyurin, a citizen of the Russian Federation," he said at a briefing in Kyiv on Monday.

"These actions (giving evidence in Ukraine) caused concern among the Kremlin top circles and according to the investigators, the FSB leadership together with Russian criminal bosses organized the killing of the man whom they see as an extremely valuable witness," Lutsenko added.