KIEV — A former Russian member of parliament who defected to Ukraine and began sharply criticizing Russian President Vladimir Putin was gunned down Thursday in Kiev in an apparent contract killing.

Ukrainian President Petro Poroshenko called the murder of Denis Voronenkov, a former member of Russia’s Communist Party who fled to Kiev in October 2016, “an act of state terrorism by Russia.”

A suspected assailant was arrested after Voronenkov was shot twice in the head, dying on the spot.

The suspect’s identity or other details were not immediately made public.

In Moscow, a Kremlin spokesman denied Russian involvement in the killing.

But Russia’s critics were likely to draw parallels between the slaying and the deaths of other Putin foes. It also raises further alarm in Washington, D.C., where Russia has come under scrutiny for allegedly trying to influence the presidential election to aid Donald Trump.

In an interview with The Washington Post on Tuesday evening – less than 72 hours before his death – Voronenkov complained about anonymous threats against him and his wife, Maria Maksakova, a former member of the United Russia party founded by Putin, with whom he fled to Kiev last year.

After receiving Ukrainian citizenship in December, he testified in the case against Viktor Yanukovych, the former Ukrainian leader who was toppled in 2014 revolution after dozens of protesters were killed in shootings in downtown Kiev.

Before fleeing Russia, Voronenkov was the target of a fraud investigation. He was formally charged in February after a high-profile interview where he compared the patriotic fervor in Russia to Nazi Germany.

Voronenkov said the charges against him over a corporate raiding case had been fabricated by his political enemies.

On Tuesday, he called the Russian state under Putin “totalitarian,” and said he had always opposed Russia’s annexation of Crimea despite having voted for it in 2014 in parliament.