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KIEV, Ukraine — A former Russian lawmaker Denis Voronenkov was shot and killed in Kiev Thursday in what the Ukrainian president described as an "act of state terrorism" by Russia, an accusation that has been quickly rejected by the Kremlin.

President Petro Poroshenko said Voronenkov's killing "clearly shows the handwriting of Russian special services shown repeatedly in various European capitals in the past."

Ukrainian police examine the body of former Russian lawmaker Denis Voronenkov after he was shot on the street in Kiev, Ukraine, on March 23. Serg Glovny / Zuma Press

In a statement released by his spokesman, Svyatoslav Tsegolko, Poroshenko described the victim as a key witness who gave testimony about "Russian aggression" to the Ukrainian authorities.

Russian President Vladimir Putin's spokesman, Dmitry Peskov, dismissed the claim of Russian involvement in the killing as "absurd" in a statement carried by Russian news agencies.

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Voronenkov, 45, a former member of the communist faction in the lower house of Russian parliament, had moved to Ukraine last fall and had been granted Ukrainian citizenship.

He testified to Ukrainian investigators as part of their probe into the activities of the nation's former Russia-friendly president, Viktor Yanukovych, who was ousted by massive protests in February 2014.

Voronenkov, who had obediently toed the Kremlin line while serving as lawmaker, became a vociferous critic of Russian policies after his move to Kiev.

Ukrainian police said Voronenkov was shot dead by an unidentified gunman near the entrance of an upscale hotel in the Ukrainian capital.

The assailant also wounded Voronenkov's bodyguard, who fired back and wounded the gunman. Police said they were both hospitalized.

Voronenkov left Russia with his wife, singer Maria Maksakova, who was also a lawmaker. He said he had to leave Russia because of persecution by Russian security agencies and had renounced Russian citizenship.

Denis Voronenkov Oleksandr Synytsia / AP, file

After Voronenkov's move to Ukraine, Russian investigators have filed fraud charges against Voronenkov in connection with his business activities.

Members of the Russian parliament were quick to reject Ukrainian allegations that Voronenkov could have been killed over any betrayal of Russia.

Nikolai Kovalyov, the former Russian security chief who is a lawmaker, told Russian state television that the killing could have been rooted in a business dispute.

Peskov said that Putin was informed about Voronenkov's killing and voiced hope that Ukrainian authorities would solve the crime. He added that Voronenkov's widow was welcome to return to Russia.