Russian former chess champion and fierce Kremlin critic Garry Kasparov said Saturday that Mikhail Khodorkovsky's release from a Russian prison was "essentially" thanks to German Chancellor Angela Merkel.

"I think merit for the freeing of Khodorkovsky essentially goes to Merkel. Her pressure played a decisive role; on that, she brought about more than the Americans," Kasparov told news weekly Focus' Online.

Khodorkovsky's stunning release from prison on Friday was worked out behind the scenes with the German government, coming about after negotiations between German former foreign minister Hans-Dietrich Genscher and Russian President Vladimir Putin.

Kasparov urged Merkel to not attend the Winter Olympics that Russia is hosting in Sochi in February.

"If she refuses, great respect is due to her," Kasparov told Focus Online. "That would be a heavy blow for (President Vladimir) Putin."

German President Joachim Gauck has said he would stay away from the Games, though he denied his absence was a "boycott" over Russia's human rights record.

Merkel this week made clear that she had no plans to attend the Olympics, stressing that in eight years as German leader she had never visited any Olympics events.

Kasparov also said that he did not see Putin's pardon of Khodorkovsky, also a Kremlin critic and ex-oil tycoon, after more than a decade in jail, as an indication of changes afoot in Russia.

"For the general situation nothing has changed," Kasparov said.