A top Senate Republican accused Russia of engaging in "state terrorism" following the murder of a prominent critic of President Vladimir Putin who had fled the country.

"Today, in yet another brazen act of Russian state terrorism, former Russia parliamentarian Denis Voronenkov was assassinated in broad daylight on the streets of Kiev," Senate Armed Services Committee chairman John McCain, R-Ariz., said Thursday.

Voronenkov, who was shot outside of his hotel days after complaining to media that he was in danger, had moved to Ukraine after stepping down from the legislature and compared Putin's Russia with Nazi Germany. He was also helping Ukrainian authorities build a treason case against former president Victor Yanukovych, a pro-Russian leader whose ouster precipitated the Russian annexation of Crimea and destabilization of eastern Ukraine.

"This horrific crime marks the continuation of a campaign of KGB-style brutality designed to intimidate anyone who dares to oppose the tyranny of Vladimir Putin," McCain said.

The former Republican presidential nominee is one of Putin's most outspoken critics, a co-author of sanctions legislation targeting corrupt foreign leaders; the bill is known as the Global Magnitsky Act, named for a lawyer who died in a Russian prison after exposing corruption by government officials. Voronenkov's death took place the same week that a lawyer working on behalf of the Magnitsky family fell from the roof an apartment building, suffering serious head injuries.

"Once in a generation, strange things happen; when they happen on a regular basis like they do in Russia, there is government complicity in this," Maryland Sen. Ben Cardin, the top Democrat on the Foreign Relations Committee, told the Washington Examiner. "These are intentional actions."

McCain's statement echoed Ukrainian President Petro Poroshenko's charge that the murder was "an act of state terrorism on the part of Russia," but Cardin didn't embrace that same language.

"That's a term that has some legitimacy," he said. "You know, terrorism is usually looked at to be random. This is certainly not random. This is certainly targeted."