A former Russian MP Denis Voronenkov was shot dead in the centre of the Ukrainian capital of Kiev, said media report on Thursday.
Denis Voronenkov, the former State Duma deputy, was testifying against Ukraine's ex-President Yanukovych.
Denis Voronenkov was killed around noon and his bodyguard was injured in the attack, Kiev police chief Andriy Kryschenko said.
Natspolitsiyi spokesman Jaroslav Trakalo said: "Yes, I can confirm that the victim - former State Duma deputy Voronenkov."
Ukrainian President Petro Poroshenko said the killing was an act of Russian "state terrorism."
It was reported in Pravda that Voronenkov was out of the hotel with his bodyguard on Thursday when an unknown person opened fire on both of them. Voronenkov died on the spot and his injured bodyguard fired in response and wounded the attacker.
Voronenkov, 45, a former member of the Communist faction in the lower house of the Russian parliament.
He had moved to Ukraine last year and was given Ukrainian citizenship.
He left Russia with his wife Maria Maksakova, who was also an MP.
Video: Former Russian MP shot dead in Kiev Ukraine
Russian lawmaker Denis Voronenkov who defected to Ukraine & criticized Putin shot dead in Kiev pic.twitter.com/4CXXDF8KZ9— Simon Ostrovsky (@SimonOstrovsky) March 23, 2017
Denis Voronenkov, one of the husband-and-wife Russian MPs who fled to Ukraine, has been shot dead in broad daylight in downtown Kiev. Christ— max seddon (@maxseddon) March 23, 2017
More details awaited.