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Some claim it's no coincidence that critics of Putin and his government have been killed or imprisoned

But the Kremlin staunchly denies accusations that it's targeting political opponents

CNN  — 

Former Russian spy Alexander Litvinenko wasn’t the first critic of President Vladimir Putin to turn up dead – or the last.

Some Putin opponents claim it isn’t a coincidence that critics of the powerful leader and his government have been killed or landed behind bars. But the Kremlin has staunchly denied accusations that it’s targeting political opponents or had anything to do with the deaths.

Here’s a look at some cases of outspoken critics of Putin’s government who’ve ended up in exile, under house arrest, behind bars or killed.

Mikhail Khodorkovsky

The business magnate backed an opposition party and accused Putin of corruption.

He spent more than 10 years behind bars on charges of tax evasion and fraud.

In statements to CNN, Khodorkovsky said his prosecution was part of a Kremlin campaign to destroy him and take control of Yukos, the oil company he built from privatization deals in the 1990s.

The Kremlin denied the accusation. At the time of Khodorkovsky’s sentencing, the Russian Foreign Ministry said in a statement that “allegations about some kind of selective prosecution in Russia are groundless. Russian courts deal with thousands of cases where entrepreneurs are prosecuted.”

Due for release in August 2014, he was released nearly a year earlier, in December 2013, after Putin signed an amnesty decree pardoning him.

His release, along with the pardoning of dissident Russian punk band Pussy Riot and a group of Greenpeace protesters, was widely seen as an attempt to improve the country’s image before the Winter Olympics in Sochi last February.

Khodorkovsky is now living in Switzerland. He told CNN’s Christiane Amanpour last month that he wants to see regime change in his country.

“I think that my country doesn’t deserve a new era of authoritarianism,” he said. “But at the same time, I don’t want a revolution.”